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Experimental determination of strain in thin aluminum plate with central hole subjected to far-field tensile loading using digital image correlation (DIC)
, Available Online: April, 2024 Angaw Chaklu Engidaw, Araya Abera Betelie and Daniel Tilahun Redda PDF (550K) |
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Abstract:
A flat Aluminum specimen with a geometric discontinuity, which allows testing of the applicability of 2D and 3D Digital Image Correlation Strain measurements, has been considered for this research since it is prone to high stress concentration via Addis Ababa Institute of Technology research interest. Experimental strain using digital image correlation and geometry measurements should be measured with estimated material properties and compare the results with theoretical model predictions. Aluminum plate with central hole were subjected for far field stress in the Machine shop of School of Mechanical and Industrial Engineering at Addis Ababa University in order to test the agreement between DIC’s strain analysis, strain gauge strain analysis and calculated empirical formulas of strain analysis and for the stress distribution of the plate elastically deformed by using VIC-3D and strain gauge. The aim is to measure vertical strain field, Vertical strain along horizontal line through hole center as function of applied loading and vertical strain using theoretical formula along same line as measurements in a plate with central hole subjected to far field and near field tensile loading using visual image coloration (VIC-3D) software, Destensometere device and solid mechanics equations to compare strain results.
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Improving mechanical properties of concrete by using fibrous materials
, Available Online: April, 2024 Omar Shahid Khan, Samiullah Sohu, Mir Zafarullah Jamali, Shakeel Ahmed and Sasitharan Nagapan PDF (550K) |
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Abstract:
Concrete is the most significant source of construction in the construction industry of the world. However, concrete causes excessive production of cement, which is one of the key contributors of carbon dioxide emissions to the environment. To minimize the use of cement in concrete, various innovative materials are being added in concrete to make it sustainable. In this study, a comparative study between three fibers Carbon Fiber, Glass Fiber, and steel fibers was done to determine which one is the most suitable fiber. For this purpose, testing on specimens was done for tensile and compressive strength at 0.5% addition of each fiber. Testing was done after 3, 7, 14, and 28 days of curing. The results spelled out that the highest compressive strength of 37.53 MPa of cube specimens was found in carbon fiber after 28 days, and Glass fibers exhibited the lowest gain in strength at about 32.335 MPa. Carbon Fiber gained 28% more strength than the control mix. On the other hand, tensile strength was also found highest in carbon fibers i.e. for the cubes the maximum difference between different fibers inducted concrete samples is 28% approximately, and for cylinders it is 27%, respectively. On the other hand, the highest tensile strength of concrete was also gained with the carbon fiber at about 3.61 MPa. The same was found lowest in glass fiber at 3.12 MPa. Carbon fiber got about 44 % improvements in tensile strength.
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Investigation of fracture characteristics of titanium/CFRP hybrid composites through experimental and numerical methods
, Available Online: March, 2024 Aysun Guven Citir, Serkan Toros and Fahrettin Ozturk PDF (550K) |
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Abstract:
In this study, the delamination resistance of carbon fiber reinforced polymers (CFRP) consolidated with titanium alloy at the interface between the metal and composite was investigated experimentally and numerically. End-notched flexure (ENF) tests were performed to assess the fracture toughness (GIIC) for Mode II crack expansion of Ti6Al4V titanium alloy/CFRP composite parts. The EFN test is applied to Ti6Al4V-carbon fiber/low melt poly (aryl ether ketone) (CF/LM-PAEK) and Ti6Al4V-carbon fiber/poly (ether ketone ketone) (CF/PEKK) composites with the [0°]24 stacking sequence of unidirectional (UD) fibers. Experimental results indicate that the LM-PAEK composites exhibited Mode II strain energy release rate values 27.64 % higher than those of the PEKK composites. The finite element simulation by LS‐DYNA shows good correlations with the experimental results, with an average error of 5.44 % for the PEKK and 10.58 % for the LM-PAEK, respectively.
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Effects of thermal conditions on fatigue behaviour of laminated glass/epoxy plates under tension-tension cycle
, Available Online: March, 2024 Madhusmita Biswal, Priyadarshi Das and Shishir Kumar Sahu PDF (550K) |
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Abstract:
The fatigue behavior study on laminated glass/epoxy composite plates at elevated temperature is attempted in the present research work. INSTRON 8862 servo-electric universal testing machine with hydraulic suspension is utilized to perform low cyclic tension-tension fatigue tests at 0.5Hz and 0.7Hz frequencies. Bluehill universal software compatible with INSTRON 8862 is employed to obtain the relationship of fatigue stress upon cycles to failure (S – N) for each specimen. The parametric investigation is done for the loading frequency, lamination sequence and number of layers to understand their effects on fatigue behavior of composite laminated plates under ambient and thermal environment. The elicited results lead to the conclusion that above parameters greatly influenced the fatigue behavior of composite laminated plates under thermal loading. The rising temperature has significant adverse effects on fatigue life. The present research is beneficial for the analysis and design of laminated composite plate or plate-like structures in the domain of fatigue analysis.
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Numerical and analytical models of the mechanism of torque and axial load transmission in a shock absorber for drilling oil, gas and geothermal wells
, Available Online: March, 2024 Serhii Landar, Andrii Velychkovych, and Vasyl Mykhailiuk PDF (550K) |
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Abstract:
The paper proposes an improved design of a shock absorber used in drilling deep oil and gas and geothermal wells with polycrystalline diamond compact (PDC) bits. The proposed innovations successfully combat the dangerous phenomenon of self-excited vibrations, which can lead to malfunctions such as stick-slip and whirling of the drilling tool. Most conventional drill shock absorbers are designed to only absorb longitudinal vibrations, which was sufficient when using roller cutter bits for the drilling process. However, the design features of PDC bits and the phenomenon of interaction of their cutters with interlayered rocks during deep drilling impose new requirements on the properties of the drill shock absorber. To protect the downhole tool from abnormal torque values and torque oscillations, it is proposed to equip the shock absorber with a special torque transmission unit in the form of a fourteen-thread self-releasing screw pair. This unit is capable of transforming increases in external torque into increases in the force that loads the elastic element of the shock absorber. The numerical and analytical models of the mechanism of transferring external axial load and torque to the elastic element of the drill shock absorber are constructed. The distribution of contact pressures on the interacting surfaces of the screw pair and the distribution of equivalent stresses in the screw pair parts are analysed. The strength of the proposed drill shock absorber assembly was evaluated using the Huber-von Mises energy criterion. The dependence of the load transmitted to the elastic element of the shock absorber on changes in the external torque and external axial force is investigated. In general, it is determined that the external load is distributed evenly between all turns of the screw pair, and the limit state of the parts of the proposed assembly is not reached even under high-torque operating load. The obtained analytical dependencies will allow to effectively determine the required strength and stiffness of the elastic element of the drill shock absorber at the design stage. The obtained analytical results were verified using a finite element model.
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Experimental study of precast concrete walls using bamboo as alternative reinforcement
, Available Online: March, 2024 Ronny Hasudungan Purba, Titis Lukita Sari, Sugito and Muhtar PDF (550K) |
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Abstract:
The public's demand for simple, livable houses means that material studies to support this continue to be carried out today, starting from using natural materials such as bamboo as precast concrete walls. This study aims to conduct an experimental study using bamboo rope from the Gigantochloa Apus variety as an alternative reinforcement for precast concrete walls. Research was carried out on 12 precast concrete wall test specimens, and the flexural properties, flexural strength, and crack patterns were formulated when subjected to a quasi-static load concentrated in the middle of the span. The concrete slab measures 600800 mm with a 50 and 75 mm thickness. The three configurations of bamboo bones used include (1) Gedhek-type woven bamboo slats, (2) bamboo slat type, and (3) Sasak-type woven bamboo slats. The research results show that Sasak-type woven bamboo slat reinforcement is the most effective alternative reinforcement. The behavior of the test specimen shows a ductile failure pattern similar to conventional reinforced concrete. The maximum moment capacity achieved is 1.5 to 2.2 times greater than the theoretical nominal moment capacity. Meanwhile, the behavior of test specimens with conventional plate-type woven bamboo slat reinforcement showed sudden and brittle failure due to slippage at the bond between the bamboo reinforcement and concrete. The average maximum moment from the test results is 60% of the theoretical nominal moment. The results of this research recommend that woven bamboo slats of the conventional plate reinforcement type are less effective as alternative reinforcement if they are not given special treatment to increase their adhesion to concrete. Gedhek-type woven bamboo slats are not effective as alternative reinforcement because they cause separation of the top and bottom parts of the woven concrete, thereby reducing the integrity of the cross-section and causing the cross-sectional capacity to be relatively small.
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A multi-criteria model approach for identifying priorities in road maintenance in the province of Lampung, Indonesia
, Available Online: February, 2024 Mulyadi Irsan, Rudy Hermawan Karsaman, Najid, Leksmono Suryo Putranto and Sugito PDF (550K) |
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Abstract:
The source of financing largely determines the implementation of road maintenance. Due to the limited funding capacity of the Regional Government, the performance of road maintenance cannot be handled throughout the provincial road network, so it is necessary to determine the priorities and types of maintenance that must be performed carefully and accurately following the conditions. Therefore, this article conducts a study to determine the priority scale in road maintenance in the province of Lampung (Indonesia), which is limited by the government's financial capacity to make comprehensive improvements through a multi-criteria analysis approach. The approach used is a survey method with purposive sampling, integrated with a multi-criteria analysis approach to find eigenvalues as a priority for improvement. There are at least eight groups with 238 respondents who provide input in determining the priority of road preservation in the province of Lampung. The results show that there are ten main parameter criteria to assess the implementation of road preservation in the Lampung province, including accessibility, social, regional development, economy, number of vehicles, security, congestion, road damage, road safety, and regional disparities. The results of the calculation of the multi-criteria analysis of the parameters found that the "road damage" parameter has the highest weight or eigenvalue. The following parameter that becomes the main consideration is the economic aspect and accessibility, with the second and third largest eigenvalues. The security parameter is a factor that is not considered because it is ranked the lowest.
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Experimental and numerical study on the load-bearing capacity, ductility and energy absorption of RC shear walls with opening containing zeolite and silica fume
, Available Online: January, 2024 Mehran Mozafarjazi and Ramin Rabiee PDF (550K) |
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Abstract:
This article originates from an experimental program and nonlinear finite element analysis aimed at examining how pozzolanic concrete influences the behavior of RC shear walls with openings. To achieve this, stress-strain diagrams, and the elastic modulus of 33 cylindrical concrete specimens, each containing varying percentages of silica fume and zeolite (ranging from 0% to 25%), were evaluated. The impact of silica fume and zeolite pozzolans on the ductility and load-bearing capacity of RC shear walls with openings was explored. This was done by analyzing the mechanical properties of the specimens and integrating them into the analytical model. Subsequently, a shear wall with conventional concrete was simulated using the finite element method (FEM). The study delved into the effects of substituting the initial concrete with pozzolanic concrete within the shear wall. Additionally, it investigated the simultaneous reduction in the diameter of the reinforcing bars employed, all in the pursuit of attaining the optimal design for these walls. The findings demonstrated that employing pozzolanic concrete in shear walls, coupled with a balanced configuration of rebar, led to heightened ductility, improved energy absorption, and an enhanced load-bearing capacity for the walls.
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Horizontal oscillations of the wood sawing support during the cutting process in a wood sawing line using a vertical bandsaw
, Available Online: January, 2024 Hoang Son, Vu Khac Bảy, Tran Van Tuong, Bui Le Hong Truong, Luong Anh Tuan, and Hoang Hai Son PDF (550K) |
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Abstract:
The wooden trolley (in the sawing line using a vertical bandsaw) during work generally moves by iron wheels on two rails placed on the concrete floor. Due to the effect of noticeable cutting force applied by the saw blade and the vehicle's uneven weight on the wheels, it causes the vehicle to vibrate during the horizontal movement, affecting the stability of the wood sawing circuit. By modeling the problem of vibration of beams located on Winkler elastic foundations, subjected to mobile concentrated loads, the article has built a system of differential equations of vibration of two rails, giving an expression to calculate the vibration amplitude of the swan plane. The influence of the flexural rigidity EI of the rails and the elastic stiffness k of foundation on the vibration amplitude of the cutting plane is studied and analyzed. The use of the Dirac Delta function and the employed analytical solution allow the designers to evaluate the accuracy and reliability of the calculated results.
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Restoration of tensile properties in cracked aluminum specimens via composite patching
, Available Online: January, 2024 Touam Lakhemissi, Rebai Billel, Derfouf Semcheddine and Messas Tidjani PDF (550K) |
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This study investigates the tensile behavior and crack repair of aluminum using fiberglass-reinforced composite patches. Tensile testing compared uncracked, pre-cracked, and repaired aluminum specimens. Pre-cracking by hole drilling decreased strength and ductility from stress concentrations. Composite patching recovered strength, with 4-ply laminates optimal. Uncracked samples failed by necking, pre-cracked by crack growth, and repaired by adhesive detachment. Results demonstrate composite patching effectively restores strength to cracked aluminum by mitigating stress concentrations when appropriately designed. Finite element modeling simulated stress reduction after patching. This work provides experimental data on composite patch performance for metal crack repair and confirms the approach as an effective strengthening technique, although further optimization is needed.
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Using the method of differential equations by quadratic to solve the free vibrations of columns under the effect of axial load and column weight
, Available Online: January, 2024 Amir Kazemi, Amir Nadi, Mohammadreza Moradi, Farzaneh Tahmoorian and Peyman Beiranvand PDF (550K) |
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Abstract:
This paper investigates various techniques used to solve the differential equations governing the free vibration of columns. The present work focuses on the study of the free vibration of Euler’s Bernoulli column of equal strength in compression, considering its own weight and the axial load in compression and tension while subjected to symmetrical boundary conditions. The investigation utilizes the differential quadrature method to examine the fifth natural frequency parameters of the column in different states of column boundary conditions and varying geometric section shapes, including pin-pin and clamp-clamp configurations. The results of this work contribute valuable insights for informed decisions on selecting the cross-section types and appropriate boundary conditions for ensuring the stability of such columns in civil constructions.
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Optimization of non-bearing splice connection in GFRP short columns by manual testing and finite element analysis
, Available Online: January, 2024 M. J. Srujan and Seelam Srikanth PDF (550K) |
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Abstract:
Connection designs are established to ensure the stability of joined cut sections, the joints so designed should be based on the optimal performance as per the requirements. The connection joints so established should not be based on just strength but reliability and durability as well. This study focuses on tackling one of the major issues faced when using Glass Fibre Reinforced Polymers (GFRPs) as construction materials, which is based on the abrupt failure of the material under critical or maximum loading. Connection designs are established in GFRP short column H-sections based on Bolted Splicing connections by Eurocode 3 for steel splicing connections. A total of seven Connection designs are established using bearing and non-bearing splicing connections. A total of five models for each connection is established for manual testing and Finite Element Analysis (FEA) is used to simulate and analyze these connection designs. Parameters such as ultimate load, displacement at ultimate load, stiffness, compressive strength, failure mode, load versus displacement behavior graph, and percentage compressive strength compared to the un-cut section are provided in this study. The strongest specimen in this study displaced 128% and 127.7% compressive strength compared to an un-cut GFRP H-section when tested using manual testing and FEA accordingly.
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Assessment of the impact of column-to-beam strength ratio on seismic response of RC beam-column connections
, Available Online: January, 2024 Mohamed Mimouni, Djamel El Ddine Kerdal and Lamia Kharroubi PDF (550K) |
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Abstract:
Beam-column joints play an important role in the overall resistanceof reinforced concrete frames during seismic events. The Earthquakes of Al Asnamon October 10, 1980, and Boumerdes on May 21, 2003 in Algeria, have highlightedthe failure of beam-column joints as a cause of building collapse. 3D nonlinearfinite element analysis with ANSYS software has been used in order to examineexterior RC beam-column joints under monotonic loading. The research has investigatedthe influence of the value of the column-to-beam strength ratio (CBSR) of thesejoints on shear strength and seismic performance of concrete structures bychanging the height and longitudinal reinforcement of the beam while keepingcolumn dimensions constant. Ithas been shown that the beam-column depth ratioand the beam longitudinal reinforcement ratio have a significant effect on theshear capacity and seismic behaviour of exterior beam-column joints. Anappropriate value of the flexural strength ratio between the column and beam iscrucial in order to establish a "strong column-weak beam" mechanism inreinforced concrete frames, because inadequate values can lead to prematurefailure or reduced shear capacity at the junction. The Algerian seismic code –RPA99/version2003 suggests a minimum value of column-to-beam strength ratioequal to 1.25 at joints for seismic design when building codes in othercountries call for higher ratios. Nevertheless,this approach might notaccurately represent the actual behaviour and could constrain the optimalperformance of structures.
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Mechanical characterization procedure of HMPE fiber for offshore mooring in deep waters
, Available Online: January, 2024 Daniel Magalhães da Cruz, Marcelo de Ávila Barreto, Larissa Basei Zangalli, Aleones José da Cruz Júnior, Ignacio Melito, Fernanda Mazuco Clain and Carlos Eduardo Marcos Guilherme PDF (550K) |
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Abstract:
For several offshore installations, especially those for exploration of offshore resources, such as Floating Production Storage and Offloading (FPSO), the stability of subsea pipelines and exploration risers are closely related to the mooring system. High performance polymeric fibers have been used in recent decades for offshore mooring, more recently polyester has been challenged by advancement in ultra-deep waters due to its considerable elongation. A candidate fiber for lower elongation mooring systems is high modulus polyethylene (HMPE). The work describes mechanical characterization procedures in high modulus polyethylene fibers envisioning the possibility of offshore mooring systems made entirely with HMPE, which allow deeper water depths, as well as stability to the pipelines. As a result, the fiber is suitable for mechanical strength and linear tenacity. It still shows good performance in abrasion resistance, and loss of inelastic portions in cyclic loads. However, the behavior in creep, due to its slightly high strain rates, restricts its use, but recent fibers known as "Low creep" can be studied, allowing complete mooring systems made with HMPE.
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Optimization of laser welded ASTM A36 mild steel with different laser beam oscillation patterns utilizing experimental and simulation data
, Available Online: January, 2024 Said Ouamer, Karim Bensalem, Asim Iltaf, Noureddine Bark and Shayan Dehghan PDF (550K) |
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Abstract:
Recently, there has been an increase in the use of laser beam welding of mild steel in various industries, including petroleum refineries, power plants, pharmaceuticals, and even residential areas. This research paper focuses on studying the effects of laser welding process parameters, such as laser power and welding speed, on the tensile strength of welds. To do this, three types of laser beam oscillations (sinusoidal path, triangular path, and square path) were performed to weld 125mm x 60 and 1.8 thick sheets of ASTM A36 mild steel alloy. The researchers used statistical tools such as ANOVA to generate mathematical models and experimental designs using the Taguchi method. The results indicate that the optimal welded joint has good mechanical properties after laser welding. For ASTM A36 mild steel, the optimal parameters for laser welding are a laser power of 1800 W, a welding speed of 50 mm/s, and triangular welding mode.
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Study on the influence of injection molding parameters on the warpage using simulation and Taguchi method
, Available Online: January, 2024 V. L. Trinh, Dung Hoang Tien and N. S. Dinh PDF (550K) |
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Injection moulding (IM) is a processing technique produced from polymeric products. Warpage defect (WD) is the defect that generally occurs during the IM process due to the inappropriate processing parameters of the melt temperature, mould surface temperature, packing pressure, injection pressure, and packing pressure time. This paper investigates the IM parameters that influence product warpage by combining the simulation, analysis of variance, signal-to-noise analysis, and Taguchi method. The simulation process was performed by Moldflow software. The product material is high-density polyethylene. The WD has been predicted and optimized to enhance product quality. Melt temperature and packing pressure time are the factors that acrimoniously influenced the warpage of the product. The results show that the packing pressure time and melt temperature have the highest effects on the WD by the contributions of 48.94% and 37.48%, respectively. The optimal IM parameters are scanned again with the WD abated at about 1.2%. The mathematical formula has been constructed to predict the WD with the reflection of acceptable values of 86.29%. The research hopes that the results have been applied to designing and fabricating the plastic product in the near future.
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