Results Of Static Tests Research Articles

Effect of surface microporous copper coatings on corrosion properties of graphene-reinforced aluminium matrix composites

ABSTRACT It is difficult to assess the temperature and pressure resistance of the existing soluble bridge plug seal ring used in fracking for shale gas reservoirs, to go with its high plasticity and good solubility. To overcome this shortcoming, aluminium matrix composites with the addition of 0%, 0.5% and 1.0% of graphene were prepared by spark plasma sintering. Uniaxial static pressure test results show that the composite has the maximum compressive strength and compression ratio when the graphene content is 0.5%. Microporous copper coatings were prepared on graphene/1070 aluminium surface by electroless plating. The synergistic effect of the surface microporous copper coating and the internal graphene on the corrosion performance of 1070 aluminium alloy was analysed by the weight loss and electrochemical methods. The results showed that the surface microporous copper coatings could significantly improve the uniform corrosion rate and pitting depth of graphene/1070 aluminium.

A study of the response of reinforced concrete frames with and without masonry infill walls to earthquake motions

In developing countries prone to frequent earthquakes, it is common practice to use masonry infill walls as partitions in reinforced concrete frame buildings. Frames with infill have smaller drift demands and smaller drift capacities relative to similar frames without infill. Whether the relative reduction in drift demand offsets the plausible reduction in drift capacity remains open to discussion. This investigation provides experimental evidence on drift demands and drift capacities for both frames with and frames without infill. To make fair comparisons, only experiments where sets of nominally identical reinforced concrete frames, at least one frame with no infill and at least one frame with infill, are considered. Because many static experiments provide evidence for the reduction in drift capacity caused by infill, the objective of the dynamic experiments described in this study is to quantify the reduction in drift demand attributed to infill. Results of dynamic tests show that frames with infill drifted no more than one-third the amount similar frames without infill drifted in simulated base motions of the same intensity. Results of static tests show that the smallest drift capacities of frames with infill were approximately one-half of the drift capacities of similar frames without infill. These two experimental observations indicate that infill reduces drift demand more than it reduces drift capacity suggesting an overall beneficial effect of the infill. Field data were used to test this idea. Based on surveys of low-rise school buildings, RC frames with more full-height infill walls tend to have less earthquake damage than frames with less infill. A convenient method to quantify the amount of infill walls in buildings is computing wall ratios defined as the ratio of cross-sectional area of masonry infill walls on ground floor to total floor area above ground floor. Projections of the field data suggest that infill wall ratios of at least 0.5% in both directions of a building reduce the likelihood of severe structural damage by 300% compared with smaller ratios. The use of infill presents an inexpensive yet effective retrofit technique, even if only for temporary use, for strengthening buildings vulnerable to earthquake damage.

An experimental study to investigate the mechanical behaviour of low plasticity fine-grained soil stabilized with different contents of lime and fly ash

ABSTRACT Shear strength, small and large strain stiffness moduli, and cyclic stiffness degradation of fine-grained soil with low plasticity (CL-ML) stabilized with different contents of lime and fly ash were investigated in this work. The results of static triaxial tests showed that adding fly ash to the soil-lime mixture increases significantly the compressive strength of the samples due to an increase in pozzolanic reactions. By varying fly ash up to 15% and lime up to 7%, an optimal composition with 5% lime and 15% fly ash was achieved, in which the shear strength was maximum. The results of the bender element tests also showed that the mixture of 5% lime and 15% fly ash has the highest maximum shear modulus. The results of the cyclic triaxial tests on the samples with the optimal composition; showed cyclic degradation of the stiffness due to the failure of cement bonds.

Constitutive model and activation recovery performance of Fe-SMA: Experimental and theoretical study

In this study, the static tensile properties, activation recovery properties, and post-activation static tensile properties of the China-made iron-based shape memory alloys (Fe-SMA) were experimentally studied and theoretically analyzed. The material parameters of the Ramberg-Osgood curve are modified based on the static tensile tests of Fe-SMA plates, leading to the proposal of a static tensile constitutive model suitable for Fe-SMA. The applicability analysis of the theoretical model indicates that the calculated curve achieves an accuracy of R2 ≥ 0.9. Subsequent activation tests revealed a locally optimal combination of pre-strain and activation temperature, which is concluded to be associated with the martensite content. Hot-rolled Fe-SMA plates demonstrate local maximum utilization when subjected to a 4% pre-strain and an activation temperature of 300 °C, resulting in a recovery stress of 314 MPa. Moreover, it has been determined that the two activation modes, namely single heating and multiple-cyclic heating, do not significantly impact the final recovery stress of hot-rolled Fe-SMA plates. Therefore, the multiple-cyclic activation of Fe-SMA can be utilized to compensate for prestress loss in practical applications. Furthermore, a comprehensive constitutive model for Fe-SMA is proposed based on the results of the post-activation static tensile tests. This model provides an accurate description of the static-tensile stress-strain relationship of Fe-SMA during pre-straining and after activation. This study focuses on investigating the constitutive relationship and activation recovery performance of Fe-SMA, providing an experimental basis, data support, and theoretical analysis for the practical application and further analysis of Fe-SMA in structural reinforcements.

Prediction of bridge structure deformation and strain based on dynamic testing and intelligent algorithms

The field load test is a direct and effective method for evaluating the performance of bridge structures. However, existing bridge field static load tests are costly and inefficient; moreover, they obstruct traffic and cause unavoidable damage to the bridge structure. As an alternative the the static load test, a random model update method based on bridge dynamic load tests and the Bayesian inference is proposed in this paper. The bridge static load test results were predicted with a high accuracy. To speed up the Bayesian method to infer the posterior probability density of the updated parameters, the Gaussian process was used in place of the finite element model, and the Bayesian inference used the Markov chain Monte Carlo method based on the delayed rejection adaptive Metropolis algorithm. First, the parameters to be modified for the bridge structure analysis model were determined based on the global sensitivity analysis method. Second, a uniform design sampling method was used to establish the Gaussian process optimization model to update the random model of the bridge structure. Finally, a reinforced concrete truss arch bridge was used to verify the correctness of the static load results of the bridge predicted by the random model update method based on dynamic load testing and Bayesian inference. The research results reveal that the prediction results of the bridge static load test based on the dynamic load test and Bayesian inference method agree with the actual test results.

The indirect effect of nectar-inhabiting yeasts on olfactory responses and longevity of two stink bug egg parasitoids

Adult parasitoids are well known to feed on sugar-rich resources such as floral nectar. Recently, an increasing body of evidence has shown that nectar is ubiquitously colonized by microorganisms and, as a consequence, microbial metabolic activity can affect several traits of floral nectar. Yet, how the fermentation of nectar by yeasts impacts the olfactory responses and performance of parasitoids is largely understudied, especially in the case of egg parasitoids. In this study, we investigated whether fermentation by the nectar yeasts Metschnikowia gruessii and M. reukaufii affects the olfactory responses of Trissolcus basalis and Ooencyrtus telenomicida, two egg parasitoid species associated with the southern green stink bug Nezara viridula. We also investigated how yeast fermentation affects the longevity and survival of the egg parasitoids. Results of static four-chamber olfactometer tests showed that nectar fermented by M. gruessii (but not by M. reukaufii) was attractive to both egg parasitoid species, whereas no significant yeast-mediated effects were found in terms of wasp longevity. Gas chromatography coupled with mass spectrometry (GC-MS) showed a clear separation of the volatile profiles among M. gruessii, M. reukaufii and non-fermented control nectar supporting the results of the insect bioassays. The results of our study highlight the need to consider the role of microbes when studying interactions between flower nectar and egg parasitoids and could have implications from a conservation biological control perspective.

Structure and operation mode of centrifugal side-throwing organic fertilizer spreader for greenhouses

A centrifugal side-throwing organic fertilizer spreader is designed to improve the versatility of organic fertilizer spreaders. A discrete-element method is used to investigate the driving layer limit height of the conveyor and the diversion of the guide vane, observe the jet and the disk distribution of organic fertilizer at different fertilizer drop positions, and determine that the gap between the fan blade and guard plate significantly affects the distribution of the organic fertilizer. A mathematical model of openings and flow rate is established using bench tests. Static tests reveal that the coefficient of variation (CV) can be optimized to 15–35%. The operation mode is investigated in dynamic tests by selecting two groups of representative static test results. Group 2 had a coefficient of variation of 15.73% at 0 mm overlap. Group 3 had a coefficient of variation of 18.52% at 1200 mm overlap. The study provides a feasible solution for the design of organic fertilizer spreaders for greenhouses.

Additive manufacturing for orthopedic implants: morphological and material characterization of SLM thin Ti6Al4V samples

In the last decades, the orthopedic industry has increasingly adopted Additive Manufacturing (AM) technologies, such as selective laser melting, to produce custom devices. Given their novelty with respect to discrete-size implants, New 2017/745 Medical Device Regulation introduced the need for safety and quality demonstration of such unique devices, a non-trivial task since no defined criteria state how to test them. In this scenario, numerical analyses can be a robust tool for the intended purposes as long as the reliability of the numerical models is verified in terms of geometry reconstruction and material assignment. The latter need has to deal with the peculiarities of AM in the production of lattice structures, distinctive features of this new generation of devices conceived to mimic bone morphology. Indeed, the struts of such structures have diameters of hundreds of microns, which approach AM accuracy limit. If, on the one hand, the issues related to AM production are well-known, on the other hand, it is not yet fully understood how to deal with them if thin struts are manufactured. Given the still questionable research area and starting from the few literature findings, this study aims to provide an exhaustive morphological and material characterization of Ti6Al4V thin struts produced by selective laser melting, supporting experimental activities with numerical analyses. The importance of investigating together their morphology and mechanical behavior will be highlighted: morphological analyses will constitute the first step to assess the quality of the manufactured samples and to correctly interpret the experimental results of static and fatigue tests. In this light, the differences with respect to the mechanical properties of both machined samples and thick AM samples will be outlined. The outcomes of this research will be fundamental for the development of reliable FE models of lattice-based devices.

Confirmation of the operational reliability of building structures at the place of their installation in the building

The article presents the results of full-scale static tests of two reinforced concrete columns arranged in different parts of a public building, the reliability of which was doubted due to the careless manufacture of concrete cubes before sending them for laboratory tests. Based on the doubts that arose, the construction of the object under construction was suspended with the requirement of convincing proof of the operational reliability of these load-bearing structures.

Проблема оценки выносливости элементов корпуса низколетящих орбитальных объектов

The paper analyzes the issue of calculating the endurance of the body of lowflying orbital objects from cyclic temperature alternating deformation beyond the limits of Hooke's law. The practical absence of direct calculation methods is stated. An indirect calculation is proposed on the basis of available experimental data on mechanical tests of samples with the «stress» parameter and an algorithm for transition from actual deformations to equivalent stresses. The calculation method is based on the use of the existing experimental fatigue curve under a symmetrical bending cycle, the results of static tensile tests at extreme cycle temperatures, and a generalization of known information about the patterns of changes in the endurance parameters of the material under consideration in relation to the conditions of cyclic temperature alternating deformation. The adequacy of the methodology is verified using the example of depressurization of the housing of the Zarya orbital module of the international space station, made of AMg6 alloy after ≈120,000 cycles of alternating temperature loading. The difference between the calculated and actual endurance of the AMg6 alloy is within the natural range of 20 % during fatigue testing.

Comparison of the bearing capacities of a small-diameter bored pile obtained from the results of field tests and numerical modeling

Abstract. The paper compares the results of modeling static soil tests with a small-diameter drill pile with the data obtained from field tests. The calculations were performed by numerical modeling using the PC software "Plaxis", which is based on the finite element method. This problem was solved in a flat (2D) formulation for an axisymmetric model, which makes it possible to analyze the stress-strain state (SSS) and the interaction of elements of the pile-soil environment system.
 Separate computational models were created for two types of piles made using different technologies: a bored- CFA pile and a drilled pile with partial soil displacement. In order to take into account the preload history in order to maximize the models' approximation to real conditions, the calculations were performed in 4 stages in accordance with the construction sequence: Stage 1 - initial stage (determination of the initial stresses in the soil massif in the natural state), Stage 2 - excavation to the design mark of the pit bottom, Stage 3 - testing of the soils with a pile by static load. Stage 4 - pile unloading. Based on the results of the calculations, the SSS and the interaction of the elements of the "pile-soil environment" system have been analyzed and compared the settlement graphs obtained from the results of the calculations with the data of field tests.
 It is shown that the use of a plane axisymmetric FEM is a sufficiently effective approach for assessing the stress-strain state and understanding the interaction of elements of the pile-soil system, as well as predicting the bearing capacity of piles for further design of the pile foundation before obtaining the results of field tests. In addition, the labor intensity and time consumption of this approach are relatively low compared to other alternative methods.
 With appropriate experience in using this approach in different soil conditions with appropriate comparison with field test data, it can be applied in the feasibility study and final decisions on the choice of a particular type of foundation.

Comparison of methods for determination the bearing capacity of piles in punched holes with broadening using the results of static load tests

In recent years, due to the increasing of urban construction extent, there has been a tendency to exhaust of territorial reserves, suitable for construction in large cities. Increasingly, it is necessary to use territories with unfavorable soil conditions for the construction of civil and industrial buildings. In such cases, various pile foundations are used, which have significant technical and economic advantages compared to foundations on a natural bases. Among the progressive designs of pile foundations, a special place is occupied by piles in punched holes with broadening (SPSu), which ensure the improvement of the physical and mechanical properties of the foundation during the production of works, as well as the reduction of material, energy and labor costs during their installation. Piles of this type are designed using the developed regulatory framework ISO 36554501-018-2009 "Design and installation of pile foundations and reinforced foundations from packed piles in punched holes". At the same time, the task of improving the quality of work on the design, arrangement, as well as the assessment and prediction of the bearing capacity of piles becomes particularly relevant. This task is solved with a high degree of accuracy by conducting large-scale tests of piles with a static load tests. These tests are carried out in real conditions of the construction site and allow to observe the changes pile`s settlement under load. The article is devoted to solving the problem of increasing the efficiency of assessing the bearing capacity of piles according to static load tests. Using the example of the test results of single SPSu, the authors of the article assess the effectiveness of the existing domestic and foreign methods for determining the bearing capacity of piles. As part of the solution of this issue, the results of the bearing capacity determining according to SP 24.13330.2021 were compared with the data obtained during the use of Davisson, Chin, De Beer, Hansen, Decourt and Eurocode 7 methods. The advantages and disadvantages of this approaches used are noted. Based on the accumulated practical experience of testing the SPSu in various ground conditions, the authors of the article proposed an alternative method of interpreting the "settlement - load" graph.

Considerations on an embedded pile’s effective length in an analytical calculation according to the commentary on the STN 73 1002 standard

The analytical model for calculating the bearing capacity of a pile, presented in the commentary to STN 73 1002 – Pile Foundations, gives a recommendation to reduce the pile’s length in the calculation of the shaft resistance. The recommendation is based on Caquot-Kérisel’s theory. Especially in the case of embedded piles, reducing a pile’s length in the calculation can cause the shaft friction of the embedded pile to be neglected, and the calculated resistance of the pile is thus significantly lower. The results of instrumented static load tests of embedded piles were analysed. The main aim of the study was to verify the validity of reducing the pile’s length in the analytical calculation of the shaft resistance. The results of the static load tests analysed did not show any reduction in the shaft friction on the embedded part of the pile. In the form of a parametric study, the effect of reducing the pile’s length in the calculation of shaft friction was analysed for different dimensions of embedded piles.

Fatigue behavior of short-headed studs embedded in Ultra-high Toughness Cementitious Composites (UHTCC)

The multi-cracking and strain-hardening capacities of Ultra-high Toughness Cementitious Composites (UHTCC) make it feasible for orthotropic steel bridge decks (OSBDs) applications to control crack width. In this composite bridge deck, shear connectors play an important role in providing good shear strength and ensuring structural service performance. To evaluate the shear resistance of short-headed studs embedded in ultra-thin UHTCC layer, three series of push-out tests were conducted in this study. The test results including shear strength, fatigue strength, failure modes, dynamic slip, stiffness degradation, plastic slip and residual mechanical properties were all considered and carefully discussed. In this study, the shear force of shear connectors was calculated and compared with current codes. The stress amplitude-fatigue life (S-N) relationship of studs was fitted by different codes. Then the empirical formulation was developed to predict the load-slip behavior and stiffness degradation of studs during fatigue loading. The relationship between plastic slip and fatigue life was established and normalized. Furthermore, based on post-fatigue static test results and test results in previous research, a new machine learning model was proposed to predict the residual shear strength of studs and contrasted with previous model. Then Analysis of Variance (ANOVA) with two parameters (i.e. load amplitude, maximum repeated force) was conducted and revealed that the peak load significantly impacted the residual shear strength of push-out specimens compared with load amplitude. Moreover, a parametric study was conducted to further investigate the degradation of studs under various working conditions. By experimental and theoretical analysis, UHTCC could fully develop the shear strength of studs embedded in ultra-thin cover thickness. And related models were established to predict the static and fatigue behavior of steel-UHTCC push-out specimen.

Determination of Mechanical Properties of Composites Based on the Static Test Results

Determination of Mechanical Properties of Composites Based on the Static Test Results

The Pedicled Sensate Osteocutaneous Groin Flap for Reconstruction of the Forearm and Hand

Background The groin flap is axial pedicled and versatile. Until now, this flap has been used with many modifications for the reconstruction of forearm and hand defects. However, this flap has not been used in forearm, hand, and thumb reconstruction as a pedicled sensate osteocutaneous flap. In this study, a pedicled sensate osteocutaneous groin flap was used for the reconstruction of composite tissue defects on the forearm, hand, and thumb. Patients and Methods A pedicled sensate osteocutaneous groin flap was used to reconstruction composite tissue defects on the forearm, hand, and thumb in 7 patients. The mean age of the patients was 42 years. The defects were located on the dorsal surface of the forearm and hand in 2 patients, the dorsal surface of the hand and finger in 2 patients, and the thumb in 3 patients. The dimensions of the flap skin paddle ranged from 7 × 11 cm to 8 × 23 cm, and the dimensions of the bone component ranged from 1 × 1.5 × 3.5 cm to 1 × 1.5 × 5 cm. The mean follow-up duration was 26 months. Results All the flaps survived. Flap debulking was performed using 3 flaps. Sensory recovery in the flaps was completed approximately 18 months after the first operation. When the results of static 2-point discrimination test and Semmes-Weinstein monofilament test were evaluated at 18 months postoperatively, it showed that protective sensation was obtained. Except for 1 patient, motion restriction did not develop in the wrist, elbow, or shoulder joints. An acceptable aesthetic result, minimal donor site deformity, and protective sensation were obtained in all patients. Conclusions The pedicled sensate osteocutaneous groin flap can be safely used in the reconstruction of forearm and hand composite tissue defects that do not have available vascular structures for free flaps in the recipient area and in thumb reconstruction where toe transfer and pollicization cannot be performed.

Verification of the Design Parameters Based on the Control Diagnostic of the Deformation Resistance of the Sub-Ballast Upper Surface

Abstract Based on the quality control diagnostics of the used base layers on the interstation railway section Palárikovo - Nové Zámky, the article analyzes the achieved results of static load tests that were carried out on the plane of the sub-ballast upper surface. The verification of the values is based on the project documentation, in which, on the basis of a previously performed geotechnical survey, the designer proposed a suitable type of structural sub-ballast layers. The design of the structural sub-ballast layers reflects the expected deformation resistance of the subgrade surface, its water regime, the railway line characteristic (speed zone), the type of construction work (reconstruction) and also takes into account the principle of conservation of natural resources (recycling of recovered ballast bed material).

Evaluation of ultimate load - bearing capacity of piles based on static compression test and pile dynamic analysis (PDA)

Determining the load bearing capacity of piles from field tests is a reliable method that allows for the verification of load carrying capacity according to theoretical calculations, thereby the ultimate load-bearing capacity of the piles can be evaluated, serving as the basis for selecting the design load-bearing capacity that is suitable for the site conditions. Among the various pile load testing methods, static compression testing is a traditional method known for its high reliability and early adoption. However, when piles are constructed at significant depths or large diameter drilled piles have higher load bearing capacities, static compression testing encounters difficulties due to the large experimental load and extends testing times. In contrast, the pile dynamic analysis method (PDA) introduced by the Case Institute of Technology in the United States in the 1960s determines the load bearing capacity of piles based on stress wave propagation theory in elastic bars. It offers several advantages, including shorter testing times and no need for static loading, making it suitable for challenging terrain conditions. Nowadays, this method is widely used and integrated into the design guidelines and testing standards of many countries. In this article, base on the results of axial static compression tests and PDA method on reinforced concrete piles and drilled piles at several real project to compare and evaluate the load bearing values of the piles and assess the reliability of the testing methods.

The correlation between static strength and fatigue strength test and simulation

In the bogie, the frame plays a vital role. It is not only the installation foundation and direct bearing structure of other components but also can transmit the excitation load from all directions. Therefore, the rationality and reliability of the frame design are particularly critical. In this work, according to EN13749, UIC615-4, JIS E 4207, and JIS E 4208 standards, the load conditions are compiled, and the finite element analysis is carried out. The static strength and fatigue strength are tested on the test bench. The results show that the static strength results of the bogie frame are less than the allowable stress of the corresponding material. The fatigue assessment was carried out by Goodman diagram, and the data all fell within the envelope, which met the requirements of fatigue assessment. Finally, the test results are compared with the simulation results. Through the correlation analysis of the static strength test results and the finite element simulation results of the frame, the stress exceeds 10% of the material yield limit under the exceptional load condition, and the large stress points of the local hanger are compared. The results show that the frame strength test results and the finite element simulation results maintain a good correlation.

Bolted joint method for composite materials using a novel fiber/metal patch as hole reinforcement—Improving both static and fatigue properties

Several joining methods exist, and these are generally categorized as bolted joining methods, adhesive bonding methods, or hybrids of the two. Over the years several joining techniques have been proposed to improve the load transfer between components. This paper presents a new bolted/pinned joining methods for composite applications. This is done by introducing a new patch-type reinforcement. Both static and fatigue test results are presented and compared with unreinforced bolted joint data. Experimental data shows that significant improvements are obtained for both static and fatigue load conditions when this new joining method is utilized. Different metrics are used in the paper to compare the performance of the presented joining methods with existing methods. These metrics are a load transferring efficiency factor, bearing stress, and percentage improvement compared to a reference sample. For most of these metrics, the presented joining method performs similarly or significantly better than existing solutions. In addition, finite element simulations highlight that the advantage of the presented joining method is that the load is not only carried by compressive stresses above the loaded hole but also by tensile stresses below the hole. Therefore a much more efficient load-transferring mechanism is created with the presented joining method.