Experimental Test Methods Research Articles

Symmetric multipath branching as a layout design strategy for blast-resilient tunnel structures

Explosions can result in massive fatalities and severe damage to structures and facilities in tunnels. Therefore, it is of crucial importance to incorporate disaster mitigation strategies against potential blast scenarios in the design of such structures and implement viable solutions to attenuate the destructive effect of blast waves caused by explosions. To this end, we propose an innovative layout design strategy called symmetric multi-path branching, where multiple closed-end paths with relatively small cross-sectional areas branch out laterally from the sides of a straight and prismatic tunnel. To exploit the neutralizing effect of colliding pressure waves, a reflective symmetry with respect to the longitudinal mid-plane of the tunnel is considered in the layout design. To examine the effectiveness and efficiency of this strategy in reducing the effect of the pressure wave caused by the explosion, a series of layout designs are produced and investigated numerically and experimentally. After verifying the simulation method, the effect of the branching angles, cross-sectional geometry, drilling depth, and location of the branches, as well as the mass of the explosive charge, are studied systematically. The results illustrate an acceptable match between the numerical and the scaled experimental test methods. Moreover, it is shown that using three pairs of branches with an appropriate geometry and branching angles can attenuate the pressure waves passing through the tunnel up to 50% without obstructing the main route. The findings of this study can be applied to designing blast-resilient layouts in the development of underground tunnels and other corridor-like structures.

EXPERIMENTS USING ABS PLASTIC SEEDS (ACRYLONITRILE BUTADIENE STYRENE) AS ADDITIONAL MATERIALS IN PORUS ASPHALT MIXTURE

Increasing the strength of the porous asphalt mixture in the field of road contraction, in this context, porous asphalt is often used as road pavement. ABS plastic pellets (Acrylonitrile Butadiene Styrene) have the same properties as asphalt, namely, thermoplastic has a penetration value equivalent to asphalt pen 60/70, plays an important role in road pavement adhesives as an alternative and has high strength and is resistant to deformation itself. The objective of the experiment was to determine the characteristics of Marshall on optimum asphalt content (KAO) and the effect of adding ABS plastic pellets on the performance of porous asphalt was reviewed based on the Marshall test, Cantabro Loss and Asphalt Flow Down. The research used experimental testing methods in the laboratory. The research was conducted with asphalt pen content of 60/70, namely 4%, 4.5%, 5%, 5.5% 6% and additional levels of ABS plastic pellets 0%, 2%, 4%, 6% and 8%. From the planned grade for the addition of ABS plastic pellets mentioned above, the optimum bitumen content is obtained, namely 6% with a VIM value at 6% content of 23.61%, for a VMA value of 27.20%, for a stability value of 924.95 kg and the flow value obtained was 3.23 mm while the MQ value was 311.15 kg/mm. with standard or parameters namely AAPA 2004(Australian Asphalt Pavement Association).

Characteristics and variation laws of electromagnetic radiation generated during explosion

AbstractThe characteristics and laws of explosive electromagnetic radiation must be clarified to investigate its interference with electronic equipment. Currently, studies pertaining to explosive electromagnetic radiation are performed via small equivalent explosive explosion tests, and conclusions regarding the regularity of electromagnetic radiation from warhead explosions are not confirmed. This study analyzes the power laws of explosion electromagnetic radiation via numerical simulations, literature comparisons, experimental testing, and other methods. The results show that the duration of the explosion electromagnetic radiation is proportional to the 1/3 power of the equivalent. The delay time is between 44 and 53 μs and is inversely proportional to the detonation velocity. The peak time is positively correlated with the 1/2 power of the equivalent. The electric field intensity of an explosive explosion is directly proportional to the 1/3 power of the equivalent, whereas the electric field intensity of a warhead explosion is positively correlated but not linearly related with the equivalent power. The spectral distribution of the electromagnetic radiation caused by different types of explosives differ significantly. The electromagnetic radiation measurement results for explosive explosions can be predicted via numerical simulation. However, the simulation results do not match the measurement data of warhead explosions, thus highlighting the necessity of warhead explosion electromagnetic measurements.

On an alternative method for testing the dynamic strength of a small space-craft structure

This article presents an analysis of the possibility of applying an alternative approach to testing the mechanical effects of the design of a small spacecraft for remote sensing of the Earth, which has an analog product that has passed a full cycle of ground experimental testing. However, despite the similar power scheme and the maximum borrowing of onboard equipment with minimal modifications, the spacecraft planned for testing has a number of significant differences. The application of the main alternative strategies in foreign and domestic practice in the ground-based experimental development of space technology is considered, their advantages and disadvantages are described. Some criteria for decision-making on the rejection of the use of traditional methods of ground-based experimental testing of space technology for mechanical effects are given. The analysis of the normative and technical documentation adopted in the domestic industry in terms of clarifying the list of development tests of spacecraft, the assumptions of applying the computational and experimental method to the development of dynamic (vibration) strength and the analysis of the design of the spacecraft planned for testing in comparison with an analog product showed that the most preferred method of testing dynamic (vibration) strength is the strategy “protocol qualifications”. In accordance with the chosen strategy, a list of tasks was defined that will clarify the nomenclature of the development tests of the research object.

Ultimate state assessment of medium-thick composite cylindrical pressure shells based on progressive damage

The ultimate strength of medium-thick composite pressure shells under hydrostatic pressure was studied by experimental test and finite element method in this paper. The ultimate strength, damage form and strain response of cylindrical shells were obtained by hydrostatic destruction test, which carried out for two T700 carbon fiber/epoxy composite cylindrical pressure shells with different length. Meanwhile, finite element models were built to predict the strength failure pressure based on the progressive damage mechanism of composite materials and its initial defects. The finite element results were in close agreement with the experimental results. A parametric study was carried out to discuss the effect of radius-length ratio and radius-thickness ratio on ultimate strength. Based on the numerical results, an empirical formula was proposed as a function of radius-length ratio and radius-thickness ratio to predict the ultimate strength of medium-thick composite pressure shells.

Adaptive active vibration control for composite laminated plate: Theory and experiments

In this paper, an analysis model of adaptive active vibration control system of composite laminated plate using macro fiber composite (MFC) piezoelectric patches is presented, and the experimental testing is carried out. Electromechanical coupling equations of the composite laminated plate are established by considering the influence of the mass and stiffness of MFC piezoelectric patches. The adaptive active vibration control scheme for composite laminated plate based on the filtered-x least mean square (FxLMS) algorithm is proposed. The accuracy of the present analysis model is validated by the results of experimental test and finite element method (FEM). It can be found that the vibration responses nearby the first and second natural frequencies of the composite laminated plate can be rapidly and greatly suppressed by the adaptive active control system and experimental test. Moreover, the dynamic responses of the composite plate under multi-frequency excitation and random excitation can be fast controlled by the presented adaptive active control system. The novelty of this work is that a theoritical analysis model of adaptive closed-loop control system based on the MFC piezoelectric patches is presented for vibration suppression of composite laminated plate, and the effectiveness of the proposed adaptive active model are validated by experimental testing.

Peran Metode Cooperative Learning Dalam Meningkatkan Kemampuan Menghafal Al-Qur’an Siswa Kelas X di MAN 2 Kabupaten Bogor

Based on the author's observations of class X MAN 2 Bogor Regency students, 70% of students still experience low Al-Qur'an memorization skills. With this data, it is necessary to improve learning about memorization. The purpose of this study was to find out whether there was a significant difference in improving the ability to memorize the Qur'an after the Cooperative Learning method was applied. The method that will be used in this study is the Quasi Experimental Test method. The form of this research design is Nonequivalent Control Group Design, namely research to find the effect of the Cooperative Learning method on the memorization ability of class X students at MAN 2 Bogor Regency. In this study the test was administered twice: first, students were given a pre-test to find out the amount of student memorization in both the control and experimental groups. Second, students are given a final test (post-test) using traditional methods in the control class and using the Cooperative Learning method in the experimental class. From the results of the test, it can be concluded that there was an increase in the ability to memorize the Al-Qur'an for class X MAN 2 Bogor Regency students who were taught by traditional methods. It was seen that the average number of memorization increased by 13.45 verses, and there was an increase in the ability to memorize the Al-Qur'an class X MAN 2 Bogor Regency who were taught by Cooperative Learning method seen from the average number of memorization increased by 17.95. Whereas in the T-test, there is a difference in the ability to memorize the Koran for class X MAN 2 students in Bogor Regency after the Cooperative Learning method is applied, it is seen that the significance is 0.000 <0.05, so it can be concluded that the Cooperative Learning method can increase the memorization of class X MAN 2 students Bogor Regency.
 Keywords: Cooperative Learning Method, Memorization Ability

Sedimentary Facies Types and Their Control of Reservoirs in the Lower Jurassic Lacustrine Facies Shale of the Lianggaoshan Formation, Northeastern Sichuan Basin, China

In recent years, new breakthroughs have been made in the field of shale oil and gas exploration in the Lower Jurassic Lianggaoshan Formation in Sichuan Basin. At present, there is a lack of systematic studies on reservoir properties and sedimentary facies of the Lianggaoshan Formation shale. Therefore, in this study, taking the Lianggaoshan Formation in Sichuan Basin as an example, the sedimentary facies types of shale reservoirs and their control over shale oil and gas are systematically studied, based on a large number of outcrops, experimental testing, logging, and seismic interpretation methods. The results show that five sedimentary microfacies are developed in the Lianggaoshan Formation in the study area, namely, semi-deep lake mud, shallow lake mud, wave-influenced shallow lake mud, delta-influenced shallow lake mud, and underwater interbranch bay microfacies. The stratum thickness of the Lianggaoshan Formation is in the range of 26–315 m, and mainly distributed in the eastern region, but rapidly thinned in the northwestern region. The sedimentary sequence framework of the Lianggaoshan Formation has been constructed. Moreover, the lithology of the Lianggaoshan Formation shale has been divided into three types, including shale, massive mudstone and silty mudstone. The brittleness index and total organic carbon (TOC) value of three types of shale show a negative correlation. Silty mudstone has the highest brittleness, while that of black shale is the lowest. For porosity and permeability, massive mudstone is better than silty mudstone, and silty mudstone is better than black shale. There are many kinds of matrix pores in the Lianggaoshan Formation shale, and the development degree of inorganic pores is higher than that of organic pores. Finally, based on the analysis of oil-bearing, pore types, physical properties and productivity, it is considered that black shale facies is the most favorable lithofacies type. The deep–semi-deep lacustrine facies belt obviously controls the shale oil enrichment of the Lianggaoshan Formation.

Adsorption of Cu (II) from Cu Standard Solution Using Expanded Perlite

The research aimed to determine the ability of expanded perlite to adsorb or remove Cu (II) metal ions in the solution. Furthermore can be used to reduce Cu levels in the aquatic environment caused by industrial and mining waste. Expanded perlite is a product of perlite resulting from heating at temperatures above 1000°C. Perlite is a volcanic product contains high silica content and a lot of water content so when heating occurs will increase the porosity and surface area that can cause adsorption. Expanded perlite sized < 1 mm can be utilized in the remediation process of mining waste because it is effective in the adsorption of ions such as Cu so as not to be in aquatic environtment. Expanded perlites, effectively used in the adsorption process, have a grain size of < 1 mm with a dose of 60 g/l. An experimental batch test method was carried out with the parameters of pH, adsorbent dose, and contact time to determine the ability of expanded perlite to adsorb Cu (II). The optimum pH in the Cu (II) metal ion adsorption process was 7 and reached equilibrium within 240 minutes. The adsorption equilibrium (chemical adsorption due to cation exchange) that can be absorbed by 1 gram of expanded perlite is 6.11 mg Cu (II), while the maximum adsorption capacity (physical adsorption due to the hydroxyl group bonded to silica has a high electronegativity value so that it can attract positively charged ions) that can be absorbed by 1 gram of expanded perlite is 1.47 mg Cu (II).

Experimental study on structural adhesive properties of aluminum plate and carbon fiber-reinforced polymer heterogeneous materials

Structural adhesive bonding between aluminum and carbon fiber-reinforced polymer (CFRP) is an important part of the vehicle's lightweight design and must ensure high strength and durability during the life of the structural member. The paper presents a precise assessment scheme to accurately and reliably infer the performance of adhesive joints through a short-term experimental test method that focuses on intrinsic and extrinsic factors affecting bond strength. The experimental results show that the surface of CFRP is polished, which is beneficial to improve the bonding quality, and the damage type transitioned from adhesion damage to substrate or cohesion damage. Aluminum alloy electrophoresis and non-electrophoresis have no significant effect on the bonding performance. Secondly, the design of the bonding nodes should be considered to bring them into a state of shear stress and be able to withstand greater loads. Meanwhile, the moderate thickness of the adhesive layer and increased bonding area serve to enhance bond reliability. In addition, various environments can cause various physical and chemical changes within structural adhesives, which can reduce the cohesive strength and durability of adhesives. This experiment is designed to select process parameters and adhesive applications for structural adhesives, which are crucial in predicting and evaluating the performance of newly developed structural adhesives and bonded joints.

Transferability of the scuffing load capacity of gear oils determined on spur gears to hypoid gears

AbstractThe scuffing load carrying capacity is a decisive design criterion in the development of gears. In addition to the gear geometry, the entire tribological system of the gearbox must also be taken into account. Besides the loads and speeds occuring during the operation of the gears, the lubricant used and its additives have a significant influence on the scuffing load carrying capacity. In particular, hypoid gears show an unfavorable combination of high sliding velocities and high contact stresses in tooth contact with regard to the failure mode scuffing. To ensure safe operation, highly additivated gear oils are generally used in hypoid transmissions. Since it is generally not possible to determine the influence of the lubricant on the load carrying capacity of gears on the basis of physical or chemical oil data alone, experimental test methods are necessary. Due to the high scuffing load carrying capacity of highly additivated hypoid oils, the limits of many test methods are reached. In order to ensure testing highly additivated hypoid oils as close as possible to their application a new hypoid scuffing test was developed. However, since spur gear scuffing test methods can be carried out more quickly and with less resource and effort, the applicability of the spur gear scuffing test S‑A10/16.6R/90 to high additivated hypoid oils is investigated. The comparability of the two test methods and the transferability of the scuffing load carrying capacity of a gear oil determined on spur gears to hypoid gears is evaluated in scope of this paper.

Prediction of Tensile Strength in Tight Sandstone Based on Well Logging Data

The tensile strength of tight sandstone reservoirs has a direct impact on crack initiation, hydraulic fracture propagation, and the connectivity between hydraulic fractures and natural fractures during hydraulic fracturing processes. To overcome the limitations of experimental testing methods and field hydraulic fracturing techniques, this study conducted Brazilian tensile strength tests to obtain tensile strength data for 16 sets of tight sandstone samples. By comparing these experimental results with well logging data, a predictive model for the tensile strength of tight sandstone was established based on geophysical well logging data, with a correlation coefficient exceeding 0.92. The research findings indicate a positive correlation between tensile strength and sample density. This study provides support for fracture design, assesses fracturability, and aids in the selection of optimal drilling locations for hydraulic fracturing operations.

Evaluating femoral augmentation to prevent geriatric hip fracture: A scoping review of experimental methods.

Various femoral augmentation designs have been investigated over the past decade for the prevention of geriatric hip fracture. The experimental methods used to evaluate the efficacy of these augmentations have not been critically evaluated or compared in terms of biofidelity, robustness, or ease of application. Such parameters have significant relevance in characterizing future clinical success. In this study we aimed to use a scoping review to summarize the experimental studies that evaluate femoral augmentation approaches, and critically evaluate commonly applied protocols and identify areas for concordance with the clinical situation. We conducted a literature search targeting studies that used experimental test methods to evaluate femoral augmentation to prevent geriatric fragility fracture. A total of 25 studies met the eligibility criteria. The most commonly investigated augmentation to date is the injection of bone cement or another material that cured in situ, and a popular subsequent method for biomechanical evaluation was to load the augmented proximal femur until fracture in a sideways fall configuration. We noted limitations in the clinical relevance of sideways fall scenarios being modeled and large variance in the concordance of many of the studies identified. Our review brings about recommendations for enhancing the fidelity of experimental methods modeling clinical sideways falls, which include an improved representation of soft tissue effects, using outcome metrics beyond load-to-failure, and applying loads inertially. Effective augmentations are encouraging for their potential to reduce the burden of hip fracture; however, the likelihood of this success is only as strong as the methods used in their evaluation.

Seismic performance and shear lag effect of T-shaped steel plate reinforced concrete composite shear wall

This research introduces an experimental test and finite element method to study the seismic performance and shear lag effect of T-shaped steel plate reinforced concrete composite shear walls (SPRCWs). Low-cycle cyclic loading tests were conducted on five T-shaped specimens and one conventional rectangular specimen, with axial compression ratio, shear span ratio, and geometric dimensions of web and flange as the primary test parameters. The test results demonstrated that the specimens showed bending, bending-shear, and shear failure modes depending on the shear span ratios, with T-shaped specimens exhibiting more satisfactory seismic behavior than the rectangular specimen. Furthermore, the T-shaped specimens showed better seismic behavior under compression in the flange than under tension. Smaller axial compression ratios and web lengths, as well as greater flange widths, resulted in better deformation capacity and energy dissipation capacity, and the bearing capacity was enhanced by increasing the axial compression ratio and web length. Test results were used to investigate the shear lag effect of T-shaped SPRCW, and a parametric study was performed using ABAQUS to examine the impact of various design parameters on the shear lag effect. The simulation results indicated that increasing the wall height and steel plate ratio in the flange, and reducing the flange width could significantly weaken the shear lag effect. In contrast, the web length and axial compression ratio have little effect on the shear lag effect.

Experimental study on impact toughness of EH36 ship steel in Arctic areas

ABSTRACT Polar ships are subjected to the ice loading. Low temperature impact toughness of ship steels is important for the ice-breaking efficiency and navigation safety of polar ships. In this paper, the impact absorption energy of EH36 steel under different temperatures, impact velocities and plate thickness is analyzed by experimental test, Taguchi and ANOVA method. The impact absorption energy was divided into crack formation and crack propagation absorption energy. The experimental results show that the impact absorption energy of EH36 steel is positively correlated with plate thickness and temperature, and negatively with impact velocity when it was in the toughness state. The order of significance ranking from high to low is thickness, temperature, and impact velocity. The ratio of the crack propagation absorption energy increases with the temperatures and reflects the impact toughness of EH36 steel. Furthermore, the best factor combination of impact toughness of EH36 steel was obtained.

Influence of Liquid CO2 Extraction and Dissolution on Coal Adsorption Characteristics

Liquid CO2 is a non-polar fluid, and the injection of CO2 fluid into a coal seam causes a strong water–rock interaction between the inorganic minerals and organic matter in the coal and acidic fluid. The minerals in the coal are thereby corroded and precipitated to different degrees, and the organic matter is dissolved and extracted, which further changes the physical and chemical properties of the coal and rock. Three kinds of coal samples with different metamorphic degrees were selected as the research objects, and the research methods of theoretical analysis and experimental testing were used to carry out the related research on the modification of coal by liquid CO2 extraction and dissolution. After the three kinds of coal samples were extracted by liquid CO2, the pore specific surface area decreased and the CO2 adsorption decreased with the increase in extraction pressure. The reduction in anthracite adsorption was greater than that of bituminous coal and lignite; after being corroded by different CO2 pressures, the adsorption capacity of bituminous coal gradually increased with the increase in corrosion pressure, and the increase in adsorption capacity of bituminous coal was larger than that of anthracite and lignite. After corrosion, bituminous coal was suitable for CO2 geological storage.

The influence of the leading-edge angle of subgrade on the aerodynamic loads of a high-speed train in a wind tunnel

Abstract The purpose of this study is to establish the correlation between the boundary layer over the subgrade and the aerodynamic loads acting on the train model in conventional wind tunnel tests. Firstly, flow characteristics around the subgrade with different leading-edge angles (15°, 30° and 45°) are investigated through the particle image velocimetry (PIV) experimental test method. Then, wind tunnel tests of the aerodynamic performance of a high-speed train are carried out. The results are compared with previous experimental data obtained by moving model tests. Results show that, due to the presence of a boundary layer, the pressure acting on the lower part of the train head decreases, while other locations are not significantly affected. This is the reason for the reduction of the aerodynamic drag and lift on the train. In addition, the reduction effects become more obvious when the thickness of the boundary layer increases. The experimental results obtained could serve as a calibration of aerodynamic forces for wind tunnel tests on high-speed trains.

Experimental study on the generation of aerosol particles and microorganisms from surgical staff in an operating room

Surgical site infections (SSIs) will result in longer patient stays and increased hospital costs. Airborne microbe-carrying particles are one of the main causes of SSIs, which mainly originate from the surface release of the surgical team. Therefore, an assessment of the amount of aerosol particles and microorganisms emitted by surgical staff is necessary. This study implemented an experimental chamber test method in a full-size operating room for four garment systems and nine movement combinations. The results presented the emission rates of particles and microorganisms released by the surgical staff as well as microbiome analysis. Larger areas of skin exposure may result in more microbial and particle emissions. The average microbial emission rates were 54.4 and 35.6 CFU/(person•min) when wearing disposable sterile surgical suit and protective clothing suit, respectively. The type and intensity of movement could also significantly affect the number of microorganisms and particles emitted. The quantitative results of microorganisms and particles emitted from surgical staff are expected to contribute to the effective prevention of SSIs.

Novel Reinforcing Techniques and Bearing Capacity Analysis for Tunnel Lining Structures with Extensive Corrosion

Affected by the erosive environment, tunnel lining concrete in the long-term service zprocess often exhibits engineering diseases such as concrete corrosion degradation and loss of strength, decreasing the stability of the tunnel lining structure and the traffic safety. Based on HTG tunnel project, the basic distribution rule of tunnel lining corrosion and macro mechanical properties of corroded concrete were explored in this paper through engineering disease site investigation. Then, on this basis, aiming at large-scale corrosion of tunnel lining structure, two reinforcement and repair schemes are proposed, corrugated steel plate reinforcement method and channel steel reinforcement method. Indoor component tests are carried out on the two reinforcement schemes. The failure characteristics and stress and deformation law of tunnel lining members after reinforcement and repair were verified. The analysis showed that the failure process of the reinforced specimens on the tensile side could be divided into the non-cracking stage and the working stage with cracks, and the cracking load and failure load of the specimens were significantly increased. The bearing capacity of the reinforced specimens was divided into the ultimate bearing capacity against cracking and the ultimate bearing capacity during failure. Finally, the calculation methods of the bearing capacity of the channel steel reinforcement method and the corrugated steel plate reinforcement method were derived. Comparative analysis shows that the results of numerical simulation, experimental testing and theoretical simplification methods are close to each other, and the maximum deviation is less than 8%. The established method for calculating the bearing capacity of corroded components after reinforcement is reliable and can be used for the design calculation of corroded lining reinforcement.

Dynamic Behavior of Concrete: A Review

Abstract: Concrete properties are the most essential and critical physical material property when reinforced concrete structures are designed. Considering potential catastrophic accidents, testing of dynamic mechanical properties of concrete is one of the most urgent stages of development. A large number of scientific experiments have shown that the dynamic mechanical properties of concrete are influenced by strain rate. This paper covers the existed researches on the dynamic mechanical characteristics of concrete. Review of the relationship between concrete's dynamic compressive strength, deformation properties, elastic modulus, and energy dissipation capacity with strain rate. The results may vary depending on the loading technique, test apparatus, specimen size, and other variables. The study of dynamic tensile behavior of concrete was uncommon due to the limitations of experimental tools and testing methods. The data returns so far have been inconsistent and even at conflict with one another. The most widely used test techniques to investigate the dynamic tensile behavior of concrete are the direct tensile test, splitting test, bending test and spalling test.