Destructive Load Research Articles

Characterization of Recovery in Asphalt Binders.

The recovery property of asphalt binders plays an important role in the performance and service life of asphalt pavements. Since the internal stress is the driving force for the recovery of asphalt binders, the accurate measurement of the internal stress is full of significance. Based on this rationale, this paper aims to measure the internal stress of asphalt binders using a creep and step-loading recovery (CSR) test and characterizing the recovery behaviors by the internal stress. One base asphalt binder and one styrene–butadiene–styrene (SBS)-modified binder are selected in this study. The key elements of the CSR test are carefully designed and its accuracy is verified in three aspects, including the loading conditions, the effect of disturbance by step-loads, and accuracy of measured internal stress. Then, a kinetics-based recovery model is proposed to evaluate and predict the recovery properties of asphalt binders from its causal relationship. The constant-rate recovery activation energy indicates a major difference with nondestructive and destructive loading conditions, while the fast-rate recovery activation energy keeps almost constant regardless of the loading conditions. After that, the healing activation energy is calculated by using the kinetics-based recovery model and the results indicate that SBS modified asphalt binder shows better healing abilities than a base binder.

Effects of Axial and Multiaxial Variable Amplitude Loading Conditions on the Fatigue Life Assessment of Automotive Steering Knuckle

In this paper, the author has attempted to investigate the effects of different loading conditions including axial and multiaxial variable amplitude loading (VAL) on the fatigue life assessment of automotive components under various maneuvers. To this end, a case study was conducted on the cast iron steering knuckle of a passenger car. In fact, the various VAL histories are entered on the three joints of knuckle, namely steering linkage, lower control arm, and MacPherson strut. However, previous studies have shown that this high super-critical component fails through the steering linkage. Moreover, the rotation of the steering linkage is the most destructive load. Hence, in this research, different loading cases such as axial (destructive load as means 1 channel), multiaxial (only relates to loading on the joint of knuckle and steering linkage means 3 channels), and full multiaxial (including all loading time histories means 9 channels) were considered. Afterward, finite element analysis was performed for each case, and fatigue life of the component was predicted under different conditions. Next, fatigue life of the component was evaluated using the time histories of stress tensor in the root of steering linkage which is extracted by transient dynamic analysis and applying probabilistic approach based on the Liu–Zenner equivalent stress criterion. Eventually, the responses from both techniques were compared in different cases. The results reveal that life predicted using two methods are slightly different. But, the results of probabilistic approach are more accurate than the results of FEM in comparison with experimental data for the axial state. Also, one of the major achievements of this study is that for the components with complex geometry and under multi-input loading like the steering knuckle, it is essential to perform fatigue analysis by considering all real conditions and cannot be only focused to the destructive loading.

Research on Vibration Reduction Compatibility for Multiple Transportation Conditions

Vibrations in the process of transportation are often neglected in product design. In order to avoid damage to acceleration sensitive equipment or components of spacecraft due to destructive transport load, vibration absorbers are usually installed in the container during spacecraft transportation. How to determine the vibration reduction scheme suitable for different payload weight has become the key point and technical difficulty in the design of vibration reduction in transportation. Aiming at this problem, the size and weight of the target product are analysed, and the vibration features of different sections of the satellite are analysed and tested. On this basis, a general vibration reduction subsystem of the container is designed, which is suitable for three kinds of satellite sections and four types of transportation conditions, and the loading distribution parameters are optimized. Transportation test data show that the vibration reduction effect of the new system for aerospace products meets the design requirements.

Method of Expanding Measurement Limits of Digital Dynamometer in Testing Strength of Moulded Peat Products

The work is carried out to survey operating quality of sod peat produced by milling-forming machines in the field. The surveillance will help make necessary changes in mining machine designs and operating modes in a timely manner. One of the most important quality parameters of sod peat is its bending strength. To evaluate it, Tver State Technical University has developed a destruction test bench. The test bench is equipped with a digital dynamometer and a strain-gauge bracket torecord the destructive load. However, the instruments are designed for 1 kN maximum load. The bending tests of moulded peat products conducted by the authors showed that the destructive load often exceeds 1 kN, which meant that the generation and measurement limits of destructive load have to be expanded within the range of equipment being available. The problem has been solved by installing additional elements in the strain- gauge bracket and making a calibration chart. The method can expand the generation and measurement limits of destructive load by more than 50 %.

ЧИСЛЕННОЕ ИССЛЕДОВАНИЕ МНОГОПУСТОТНЫХ ПАНЕЛЕЙ ПЕРЕКРЫТИЯ РАЗЛИЧНЫХ ДЛИН

It is known that multi-cavity panels are represented in the form of I-beams (t-beams) for simplification of calculations and are calculated according to the beam theory. However, this representation can still distort the results of calculations. The purpose of this work is to study how the cross section of multi-cavity panels is represented for the samples of different length, determining the effect of the above factors on the load-bearing and deformative capacity, as well as the load of cracking. We have considered the samples of panels of various length, freely supported and working on a bend, with a cross section in a natural form, in comparison with samples of similar length in an I-beam form. The load has been applied sequentially to the samples in increments of 1 kN, until the yield point of the reinforcement in the stretched zone has been reached. A numerical study of multi-cavity panels in a nonlinear setting, with the formation of a plastic hinge in the middle of the span, has been performed. Load-deflection graphs have been obtained for modeling of the corresponding length of the samples with a natural and I-beam cross-section. The results have been obtained and compared for the load of cracks and deflections in the middle of the span under a destructive load. It has been discovered that the panel length affects the results of calculations of the forms under consideration, and the shorter the length, the more pronounced the deviation in the load-deflection graphs. As the length of the samples increases, the correlation coefficient increases and tends to one, what indicates to an increase in the relationship between the load-deflection graphs. The correction coefficients have been proposed to clarify the calculations of plates for the formation of cracks, deformations and destructive loads

Testing Epoxy Strength: The High Strength Claims of Selleys’s Araldite Epoxy Glues

Epoxy resin is a type of thermosetting polymer that is considered among the best matrix materials with excellent properties including high flexibility, good dielectrics, chemical inertness, and water repellency. The strength of epoxy can be influenced by crosslinked density and the incorporation of a variety of solid particles of butadiene. It is important to understand the techniques used to improve the adhesion strength of the epoxy resin, especially for consumer applications such as repairing car parts, bonding aluminum sheeting, and repairing furniture or applications within the aviation or civil industry. Selleys is a well-known Australian company specializing in cleaning products, adhesives and sealants; their Araldite epoxy makes specific strength claims emphasizing that the load or weight that can be supported by the adhesive is 72 kg/cm2. Our experiment aimed to test the strength claims of Selley’s Araldite Epoxy by gluing two steel adhesion surfaces: a steel tube and bracket. Altogether, a 55 mm surface was used, meaning the load held by the brackets would be 41.25 kg. Loads were added to the bracket as a destructive tensile load test were conducted. To avoid batch effect, three tubes of Selleys’s Araldite epoxy were used. Our results showed that there was a significant difference between actual load and the expected load (41.25 kg) (a two-tailed t-test with p -value < 0.05 with a fracture stress ranging from 0.019 MPa-0.095 MPa, disputing the claim that Selleys’s Araldite epoxy can hold up to 72 kg/cm2 a s we expected the p -value to be > 0.05 in order to accept the claim. The experiment showed that there is a lack of consideration by Selleys for adhesion loss mechanisms and environmental factors when accounting for consumer use of the product leading to disputable claims.

ПРОЧНОСТЬ ЖЕЛЕЗОБЕТОННЫХ ЭЛЕМЕНТОВ ПРЯМОУГОЛЬНОГО ПРОФИЛЯ ПРИ КОСОМ ВНЕЦЕНТРЕННОМ СЖАТИИ С ПРИМЕНЕНИЕМ НЕЛИНЕЙНОЙ ДЕФОРМАЦИОННОЙ МОДЕЛИ

The study of the literature showed the absence of a detailed algorithm for calculating the strength of reinforced concrete elements of a rectangular profile under oblique out-of-center compression using a nonlinear deformation model. This article, which presents such an algorithm, is intended to fill this gap. The peculiarity of the proposed method is that a local coordinate system is introduced for each component of the reinforced concrete section (concrete platform, reinforcing bar) with the beginning of the report located on the neutral axis of the section. This makes it possible to equate the longitudinal deformations to zero, e 0 =0, on this axis, and significantly simplify the formulas for determining the curvature and other parameters. The results of calculating the destructive load of Nult using the method are compared with the experimental data presented in the work of M. S. Toryanik. The comparison was made for 7 short samples that differ in cross-section size, reinforcement, concrete class, and load application eccentricity. The similarity of the results is established, the difference is from -6.8 to +6.1 %, which can be considered acceptable, so the proposed method is recommended for implementation in the design standards.

Stress-strain state of the "combined tower-reinforced concrete foundation-foundation soil" system for high-rise structures

The aim of the work was to evaluate the effectiveness of the "combined tower-reinforced concrete foundation-foundation soil" system for high-rise structures on the example of a wind power plant (wind turbine) with a capacity of 1.5-2.0 MW using computer modeling in the PC "Ansys". Thus, under the combined tower the article refers to a high-rise building, consisting of two parts: the lower composite, the upper – in the form of a thin-walled core-shell closed profile. In both cases, the shell is a pipe with a weak taper. As an analogue, the VEU considered in foreign literature is adopted: the radius of the rotor is R=41 m, the height to the axis of the wind wheel is zhub =80 m, the shell is made of high-strength C355 steel and unlike the analog in this work the cavity of the tower lower part to a height of 20 m was filled with B60 class concrete. The modeling took into account the spatial work of the elements of the structural system and the physical nonlinearity of the materials from which they are made. At the same time, the Mises strength theory was used for steel, the Williams – Varnake theory - for concrete, and the Drukker – Prager theory - for the foundation soil. Comparison of the calculation results with the analogue showed that the destructive load of the tower increased by 37% due to filling the lower part of it with concrete, which indicates the effectiveness of the proposed solution. In this case, the destruction of the tower with a concrete core and without it occurred from the loss of steel shell local stability at the level of the tower junction with the foundation (with a compressed zone).

Increasing the Bearing Capacity and Operational Reliability of Wooden Structures with Additional Elements

The article describes the main advantages and disadvantages of wooden structures, considers the main methods for improving their operational reliability as well as ways to solve the problem of reducing the material consumption of wooden structures. The indicator determining the efficiency of using material resources and, therefore, the economy of the structure, the level of methods of design, production and operation of structures is the safety factor. Its acceptable value is determined based on the experience of design and operation, and is found as the ratio of the destructive load to the design load-bearing capacity. The article, based on the analysis of design and construction experience, discusses some structural methods and methods to improve the reliability and durability of wooden building structures, such as reinforcement and the use of a set of perforated fasteners in the form of corners, plates and supports. The elements of structures and technologies for manufacturing wooden building structures using reinforcement, as well as using various types of fasteners, considered in this work, are of the greatest interest and are relevant in modern construction both when designing new structures, and during repair, restoration and reinforcement.

Strength and deformation property enhancement of compressed steel tube-concrete elements using super concrete and thin-shell structure

The article analyzes the changes in the strength and deformation property of compressed steel tube-concrete elements when the quality indicators of the original concrete (strength class for axial compression) and the metal shell are changed. The methodology of testing for central compression of steel tube – concrete columns with a core of ordinary and super concrete with a thin-shell structure is described. Comparative dependences of the relative deformations in the axial and circumferential directions depending on the relative loading levels, destructive load values for samples from ordinary and super concrete are presented. According to the results of the research, it was determined that with an increase in the class of concrete, the efficiency ratio of the concrete is reduced by an average of 12%, however, the increase in bearing capacity remains quite noticeable. In addition, the use of high-strength concrete class C80 increases the deformability by about 10% compared with concrete class C40 steel-concrete columns, with significant savings in metal.

Flexural properties of a novel foam core sandwich structure reinforced by stiffeners

The purpose of this paper is to investigate the flexural properties of a novel foam core sandwich structure with stiffeners. 3-point bending tests of two load levels were performed on three stiffened specimens (220 mm × 74 mm × 28.2 mm) and three unstiffened specimens (220 mm × 74 mm × 27.4 mm). Mechanical tests were firstly conducted under 1kN to determine the flexural and shear stiffness, and then under the destructive load to research the ultimate carrying capacity and failure modes. The skins of the specimens are fiberglass and vinyl resin, and the core is PVC foam. The mechanism of this novel structure was studied using Allen’s theory on antiplane core and thick faces. Tests indicated that, without increase in weight, shear stiffness of the stiffened specimens increased by 25% and total deflection decreased by 19%. After inserting stiffeners, the failure mode changed from indentation failure to core shear and the ultimate load increased from 2.11kN to 2.74kN. The ultimate load and failure modes obtained from theoretical prediction and FEA both showed good correlations with experimental results.

THE EXPERIMENTAL RESEARCHES OF REINFORCED CONCRETE I-BEAM ELEMENTS WITH NORMAL CRACKS WHEN TURNING

The data of experimental researches of the rigidity of reinforced concrete I-beam elements with normal cracks at the action on them of the twisting moment have resulted in this paper. It is shown that the dependence "torque-twist angle" is almost linear. Significant nonlinear deformations appear in the last stages of loading before failure. Therefore at normative torques, it is recommended to consider the work of reinforced concrete elements of the I-beam cross-section with normal cracks linear. It is shown that the presence of longitudinal reinforcement affects the strength and rigidity of beams with normal cracks. Quite a large part of the external torque is perceived by the pin forces in the longitudinal reinforcement. The difference between the external torque and the moment of the pin forces in the armature is perceived by the upper shelf of the I-beam element. In the absence of longitudinal reinforcement, the upper shelf can collapse at loads much smaller than the destructive load of beams with longitudinal reinforcement.

Safety analysis of existing masonry arch bridges by nonlinear finite element simulations

In order to simulate the specific load-carrying behavior of masonry arch bridges, nonlinear finite element analyses may be carried out. To that end, an associated analysis concept is proposed in this paper. The applied smeared crack model allows one to realistically reproduce characteristic damage patterns observed at existing bridge structures of this type. By using the proposed analysis concept, load-bearing reserves may be revealed and possible causes for existing damage may be identified. The concept includes appropriate failure criteria and corresponding safety margins. The latter approximately conform to valid design codes, but also account for the specifics of nonlinear analyses. In parametric studies, the objectivity of the analysis results and influences of different material parameters on the load-bearing behavior were investigated. Furthermore, two examples of the safety evaluation of existing masonry arch bridges are presented. In both cases, observed damage patterns could be reproduced in the numerical simulations. Destructive load tests at a disused bridge provided an additional opportunity to validate the proposed analysis concept.

Method for Construction, Maintenance, and Management of Rigid-Frame Bridges Using H-Shaped Steel Girders

This work outlines an actual case study performed on a rigid-frame bridge using H-shaped steel girders in the laboratory and introduces the process of construction, maintenance, and management of the proposed bridge structure in practical cases. A novel structural rigid connection was developed for H-shaped steel girders and reinforcing bars at the corner of the rigid-frame structure. Additionally, a full-size model of the reinforced concrete rigid-frame bridge with H-shaped steel girders was constructed and subjected to destructive loading tests to evaluate the structural integrity of the proposed rigid connection and to reveal the load-carrying capacity and failure mode of the bridge. As a result of the loading test, compression failure occurred on the upper surface of the concrete deck at midspan, whereas plasticization and breakage of the fixing nut did not occur in the vicinity of the fixing part. Therefore, the feasibility of the connection approach at the rigid corner was verified experimentally. In addition, the results of cost analysis showed that the rigid-frame bridge could potentially provide significant cost benefits compared to the other bridge structures considered in this study. Notably, regarding the total cost for a life cycle of 100 years, the overall cost of rigid-frame bridges was estimated to be approximately 0.49–0.58 of the total expenses for slab bridges. Finally, this work introduced a scheduled inspection procedure with new inspection items corresponding to the proposed bridges by utilizing visual observation in combination with other testing techniques.

LABORATORY STUDY OF STRENGTH CHARACTERISTICS GLASS-FIBER REINFORCED LIGHT-CURED COMPOSITE

Abstract. Resin-bonded bridges (RBB), which are made by the direct method are widely used to restore the integrity of the dentition. There is no common opinion regarding the optimal design of the retention elements of such prosthetics.
 Purpose is to study the influence of the design RBB supporting elements on the mechanical strength of fixing light-cured composite material, reinforced with glass-fiber tape and bulk, to the hard tissues of the teeth in laboratory conditions,.
 Materials and methods. The study was conducted on 20 laboratory samples. Extracted intact lower third molars were sprayed into halves in a transverse direction on two fragments. Each of the fragments was fixed in fast-hardening plastic so that the contact surface of the fragment of the removed tooth stood 2 mm above the plastic level, with the surface of the enamel, which was a circle, with a diameter of 4-5 mm, and was free. Samples were divided into 2 groups of 10 in each. In samples of group I, the preparation of an approximate surface of a tooth fragment was made in the form of a box-shaped cavity with rounded corners and a minimal conicality of vertical walls with the following parameters: length - 3 mm, width - 3 mm, depth - 2 mm. Reference cavities in the samples of the second group were prepared according to the proposed method, after preparation of the classical box-shaped cavity with parameters: length - 3 mm, width - 3 mm, depth - 2 mm, created additional retention elements in the form of dives located in the lower third each of the vertical walls of the cavities using special marking burs with height and thickness of the working part by 1 mm.
 In order to determine the strength of the light-cured composite fixation, reinforced by glass-fiber tape and bulk, developed device for investigating the maximum destructive loading of the samples by the shear method was used. The destructive load was measured using a dynamometer installed in the test vehicle to within 0.1 N. In addition, the specific strength of the samples was determined as the ratio of the destructive load to the surface area of the fracture or separation, and the safety margin, as the ratio of the destructive load to the mean the value of the chewing load in the area of molars taken for 150 N.
 Results and discussion. During conducting ofd the laboratory study of fixation strength of light-cured composite, reinforced by glass-fiber tape and bulk, to solid teeth tissues with different design retention elements there were found that the maximum destructive load and specific strength of the different sample groups were significantly different (p <0,01). Indicators of destructive loading of samples of the 1st group were ranged from 576.5 N to 835.9 N and amounted to an average of 771.8+90.1 N. At the same time, the destructive loading for samples of the II group was from 2425.0 N to 2999.0 N with an average of 2805.9+191.4 N. Thus, the samples of the second group had almost 4 times the magnitude of the maximum destructive load than the values of group І samples.
 The indexes of the specific strength of light-cured composite fixing to the hard tissues of the supporting teeth were also higher in the samples of the second group, their values were ​​ranged from 341.1 N / mm2 to 421.8 N / mm2 with an average value of 394.5+26.8 N/mm2. In samples from Group I, these figures were ranged from 23.1 N/mm2 to 33.4 N/mm2 and amounted to 28.6+3.3 N/mm2 on average, they were 14 times smaller than II group indicators.
 Conclusion. As a result of the laboratory study, it was found that samples of the second group with the proposed design of retention elements had higher characteristics of the strength of fixation to the hard teeth tissues than those of group I with the "classic" box-shaped form of retention cavities. Destruction of samples of the second group occurred at a significant load that greatly exceeded that which occured in clinical conditions and at a distance from the retention elements, created according to the proposed design, due to insufficient physical and mechanical parameters of the light-cured composite and reinforcing fiberglass elements. The use of the proposed preparation option will reduce the risk of failure of the fixation and improve the prognosis for the long-term exploitation of resin-bonded bridges made by direct method.

A comprehensive biomechanical analysis of sacral alar iliac fixation: an in vitro human cadaveric model.

In BriefIn this in vitro investigation, we compared the multidirectional flexibility properties of sacral alar iliac fixation with conventional methods of sacral and sacroiliac fixation using nondestructive and destructive investigative methods. The study demonstrated that S1-2 sacral fixation alone significantly increases sacroiliac motion under all loading modalities, while sacral alar iliac fixation reduced motion in axial rotation at the sacroiliac joint and offers potential advantages of a lower instrumentation profile and ease of assembly compared to conventional sacroiliac screw instrumentation.

Experimental Strength Analysis of Riveted Joints Using Blind Rivets

Abstract This article presents results of experimental investigations of the lap blind riveted joint. The main goal of the work is determination of destructive load of the blind riveted joints. The blind rivets were originally used in the aircraft structures where access to both sides of the riveted structure is impossible. Blind rivets are now commonly used in many branches of industry because of their low cost. Moreover, the riveting process is uncomplicated. There are many publications about analysis of strength of solid rivets in the research literature. However, the strength analysis of the blind rivets was rarely undertaken. There is the research gap in the analysis of both the strength and the load capacity of blind riveted joints. The influence of selected geometrical parameters of the joint on the stress distribution and the destructive force was not widely described in literature. The first part of the work presents a review of standards and publications related to stress and strength analysis of blind riveted joints. The next part of the study describes experimental investigations of joints. The examined specimens were made out of AW 2017 aluminum alloy, cut from 1 [mm] thick sheet. Investigated blind rivets were made out of aluminum alloy. The lap joint with one rivet and the single row five-rivet joint were investigated. Moreover, the different size of hole chamfer were considered. The experimental tests were performed with the use of Zwick-Roell tension machine. The main results of experimental investigations are ultimate shear load diagrams. The influence of both the hole chamfer and the number of rivets on destructive force and shear diagrams of blind riveted joints were in detail analysed. After shear tests, the fractured rivets were magnified in order to explain the failure phenomenon of blind rivets. In the future research works the obtained results will be used in strength analysis of the blind riveted joints using the finite element method.

Improvement of the crushing effect of waste printed circuit boards by co-heating swelling with organic solvent

The crushing is a crucial unit operation for recycling waste printed circuit boards. In this study, dimethylacetamide was used to improve the crushing efficiency of waste printed circuit boards. The sectional morphology of the printed circuit boards was observed by scanning electron microscopy after a swelling treatment, the result showed the metal-nonmetal interface appeared noticeable cracks. The mechanical properties of material was measured by dynamometer, the results indicated that the destructive load of treated printed circuit boards was reduced by 115.32 N. The yield and metal grade of the crushed products were determined for each fraction. For the −0.074 mm fraction, the swelling treatment reduced the yield by 8.19% versus the regular treatment. For the −0.5 + 0.25 mm fraction, the grade of copper was increased by 7.35% after the swelling treatment. In addition, the main trace elements of the electrical components can be enriched in the coarse fraction. An analysis of the infrared spectra of the organic solvent before and after the swelling treatment revealed that the compositions of the organic solvent and the resins remained unchanged with this treatment. The swelling process of printed circuit boards was illustrated by the non-uniform effects of thermal expansion of materials and the interaction of organic solvent with nonmetal. Further, the hydrogen bonds between the dimethylacetamide and the resin molecules were expressed by a molecular structure diagram. Overall, this method can achieve metal liberation and enrichment in the coarse fraction, reducing the generation of fine particles and organic solvent can also be recycled. Thus, this study provides an alternative approach to improve the crushing efficiency of waste printed circuit boards.

Hydrogen impact on the origin and propagation of welded cold cracks in low-alloy steels at low temperatures

Abstract This article presents the results of the experiment on the hydrogen influence on the appearance and distribution of cold cracks in the joints of low-alloyed steel. The increase hydrogen diffusion of in the weld metal reduces its capacity to plastic warping. The work of origin and propagation of cracks is greatly reduced with an increase in the amount of diffusive hydrogen in the weld metal. Increasing the cooling rate of the weld further reduces the ultimate destructive load. Welding at low air temperatures and high concentration of diffusion hydrogen in the weld seam increases the critical temperature of fragility.

Borate Inorganic Cross-Linked Durable Graphene Oxide Membrane Preparation and Membrane Fouling Control.

Graphene oxide (GO) membranes have the potential to be next-generation membranes. However, the GO layer easily swells in water and risks shedding during the long-term filtration. Organic GO interlayer organic cross-linking agent was not resistant to oxidation, which limits the application scope of GO membrane. In this study, an inorganic cross-linked GO membrane was prepared via the reaction of sodium tetraborate and GO hydroxyl groups, and a -B-O-C- cross-linking bond was detected by X-ray photoelectron spectroscopy (XPS). Additionally, a new atomic force microscope scratch method to evaluate the cross-linking force of a nanoscale GO layer was proposed. It showed that the critical destructive load of the inorganic cross-linked GO membrane increased from 8 to 80 nN, which was a 10-fold increase from that of the nonlinked sample. During the NaOH/sodium dodecyl sulfate (SDS) destructive wash tests, morphology, flux and retention rate of inorganic cross-linked GO remained stable while the comparative membranes showed significant destruction. At the same time, based on the better oxidation resistance, organic membrane fouling was effectively controlled by the introduction of trace ·OH radicals. This study provides a new perspective for GO membrane preparation, interlayer cross-linking force testing and membrane fouling control.