Displacement Values Research Articles

Effect of phthalate-free plasticizer addition on thermal, mechanical, and aging properties of nitrile rubber (NBR)

Nitrile rubber (NBR) is widely used in the automotive, aerospace, and chemical sectors due to its resistance to fuels, oil, thermal aging, and fatigue. A typical NBR compound is prepared with several components that are added to obtain a product to meet specific industry requirements. Plasticizer is one of the main components used in NBR compounds. Typically, phthalates like DBP (dibutyl phthalate) or DOP (dioctyl phthalate) are used for NBR plasticization. However, these phthalates-based plasticizers are associated with toxicity and often prohibited by international regulatory standards. In this way, in the pursuit of a non-toxic NBR compound, the use of phthalate-free plasticizer, namely dioctyl terephthalate (DOTP), has been proposed. In this work, NBR compounds with DOTP, DBP, or DOP were processed in an open mill and vulcanized in hydraulic press. The unvulcanized samples were tested in a moving die rheometer (MDR). Subsequently, thermal, mechanical, and aging analyses were conducted for the vulcanized samples. The lowest torque observed in the rheometric curve, the displacement value of glass transition temperature (Tg), the smaller Shore A hardness, and the high elongation at break indicate that the addition of DOTP results in higher plasticization. The better-aging properties indicate lower migration of the DOTP plasticizer. Thus, the use of DOTP as a plasticizer holds promise as a viable alternative to replace the phthalates-based plasticizer in NBR compounds.

A Study on the Results of Risk Analyses Applying the Concept of Rock Mass Stand-Up Time for Underground Mining Sites

Throughout all the countries in the world, including Vietnam, nations with well-established mining industries have undertaken extensive research on the stability of rock masses when constructing underground tunnels in varied geological conditions. The present study aims to provide a comprehensive overview of the risk assessment related to rock masses during the construction of pit lines in mining operations. Consequently, the standing time of unsupported tunnels is assessed based on different values of the strength index and deformation characteristics of the rock mass. The objective was to perform both experimental and theoretical investigations to analyse how the stand-up time of rock masses surrounding a tunnel affects the unsupported span. The analyses were based on considering the rock parameters, including strain modulus; geological strength index; and allowable displacement values, and consideration of hereditary creep properties. By examining tunnels excavated in rock strata, it was concluded that varying geological strength index values resulted in distinct creep behaviour in the surrounding rock masses. Thus, it was reasonable to compute the unsupported span and stand-up time of tunnels. The research revealed that permissible displacements are significantly influenced by the types of rock materials surrounding the tunnel structure. Recognising the significance of time, the authors introduce a more practical interpretation and evaluation of the stability of rock masses, thus enhancing the precision of commonly available models.

Atomic-Scale Dislocation Structure Evolution and Crystal Ordering Analysis of Melting and Crystallization Microprocesses in Laser Powder Bed Melting of γ-TiAl Alloys

Laser Powder Bed Fusion (LPBF) technology exhibits significant advantages in the manufacturing of components with high dimensional accuracy and intricate internal cavities. However, due to the inherent room-temperature brittleness and high-temperature gradient induced by the laser forming process, the LPBF fabrication of γ-TiAl alloy is often accompanied by the initiation and propagation of defects. The aim of this study is to investigate the forming process of γ-TiAl alloy by the LPBF method through molecular dynamics simulation, and to explain the microparticle arrangement and displacement evolution of the melting and crystallization processes, thus elucidating the link between the variations in the laser process parameters and defect generation during microscopic laser heating. The results show that during the melting process, the peaks of the radial distribution function (RDF) decrease rapidly or even disappear due to laser heating, and the atomic disorder is increased. Although subsequent cooling crystallization reorders the atomic arrangement, the peak value of the RDF after crystallization is still 19.3% lower than that of the original structure. By setting different laser powers (200–800 eV/ps) and scanning speeds (0.2–0.8 Å/ps), the effects of various process parameters on microforming and defect evolution are clarified. When the laser power increases from 200 to 400 eV/ps, the stable value of atomic displacement rises from 6.66 to 320.87, while it rises from 300.54 to 550.14 when the scanning speed is attenuated from 0.8 to 0.4 Å/ps, which indicates that, compared with the scanning speed, the atomic mean-square displacements are relatively more sensitive to the fluctuation of laser power. Dislocation analysis reveals that a higher laser power significantly increases the cooling rate during the forming process, which further aggravates the generation and expansion of dislocation defects.

Double-Row Achilles Insertional Repair With Rip-Stop Increases Construct Strength Compared to Traditional Techniques: A Biomechanical Study.

Although double-row suture-anchored (DRSA) techniques for Achilles insertional tendinosis has proven successful, a reoccurring failure mode not yet addressed is suture tearing through the tendon. This study aims to address suture tearing by incorporating a rip-stop element. Authors hypothesized that the Rip-Stop group would demonstrate increased strength compared with more traditional techniques. 12 paired cadaveric feet were used in this study (n = 24). One sample from each pair was assigned to receive the standard double-row (SDR) Achilles repair with 4.75-mm knotless anchors (n = 12). The control's matched sides were divided between 2 DRSA bridge groups: modified double-row (MDR) bridge with 3.9-mm anchors or rip-stop double-row (RS-DR) bridge repair with soft proximal anchors and 3.9-mm anchored distal row. In neutral position, specimens underwent 1000 cycles (20-100 N) followed by load to failure. Displacements, stiffness, ultimate load, and failure mode were recorded. RS-DR had the lowest initial displacement values followed by SDR and MDR (1.3 ± 0.4, 2.7 ± 1.4, and 3.2 ± 1.3 mm, respectively). Significance was detected when comparing initial displacement of RS-DR to MDR (P = .038). Cyclic displacement was lowest for RS-DR, followed by MDR and SDR (1.6 ± 0.9, 2.2 ± 1.1, and 4.5 ± 3.2 mm, respectively). Cyclic stiffness was similar for RS-DR and MDR (89.1 ± 24.6 and 81.9 ± 5.6 N/mm, respectively). RS-DR ultimate load (1116.8 ± 405.7 N) was statistically greater than SDR (465.6 ± 352.7, P = .003). RS-DR-repaired specimens demonstrated a decrease in displacement values and increased ultimate load and stiffness when compared to other groups. Results of this cadaveric model suggest that the addition of a rip-stop to DRSA Achilles repair is more impactful than anchor size. Limitations include that this was a time-zero biomechanical study, which cannot simulate the performance of the repairs during postoperative healing and recovery. A rip-stop technique for Achilles repair effectively improves dynamic mechanical characteristics and may mitigate suture tearing through tendon in a patient cohort.

Machine learning tool for the prediction of electrode wear effect on the quality of resistance spot welds

The quality of resistance spot welding (RSW) joints is strongly affected by the condition of the electrodes. This work develops a machine learning-based tool to automatically assess the influence of electrode wear on the quality of RSW welds. Two different experimental campaigns were performed to evaluate the effect of electrode wear on the mechanical strength of spot welds. The resulting failure load of the joints has been used to define the weld quality classes of the machine learning tool, while data from electrode displacement and electrode force sensors, embedded in the welding machine, have been processed to identify the predictors of the tool. Some machine learning algorithms have been tested. The most performing algorithm, i.e., the neural network, achieved an accuracy of 90%. This work provides important theoretical and practical contributions. First, the decreasing thermal expansion of the weld nugget as the electrode degradation advances results in a strong correlation between the difference of the maximum displacement value and the last value recorded during the welding and the relative failure load. Then, this work offers a practical decision support tool for manufacturers. In fact, the automatic detection of low-quality welds allows to reduce or eliminate unnecessary redundant welds, which are performed to compensate for the uncertainty of electrode wear. This leads to savings in time, energy, and resources for manufacturers. Finally, general recommendations for the timing of redressing or replacing the electrode are provided in the manuscript based on the company willingness to accept some non-compliant welds or not.

Study on the resistance of UHMWPE laminates against oblique penetration of projectiles

AbstractTo solve the problem of the wall panel of high‐performance shelters protecting against the oblique penetration of projectiles, ballistic experiments were carried out with ultra‐high molecular weight polyethylene (UHMWPE) laminates subjected to normal penetration by high‐velocity projectiles, and the deformation and failure characteristics of UHMWPE laminates were analyzed. The numerical model of the resistance of UHMWPE laminates against penetration of projectiles was established by using the finite element program LS‐DYNA. The validity of the numerical model was verified by the experimental results of damage morphology and the depth of depression of the target plate and the deformation of the warhead. On this basis, the ricochet angle and failure mode of the UHMWPE target plate against projectile penetration were studied numerically, and the impact of the angle of incidence on the residual kinetic energy and normal penetration displacement of the bullet, as well as the damage morphology of the UHMWPE target plate, was revealed by using simulation. The results showed that the ricochet angle of the bullet obliquely penetrating into the UHMWPE target plate was in the range of 45° to 50°; at the initial stage of projectile penetration, the shear fracture failure of the fiber layer mainly occurred at the striking face of the UHMWPE target plate. Under the impact of the warhead deformation, with the reduction of the residual velocity of the bullet, the failure mode gradually changed to the tensile and interlaminar cohesion failure of the fiber layer near the back face; When the angle of incidence was greater than the ricochet angle, the residual kinetic energy of the projectile increased slowly with the increase of the angle of incidence of the bullet and then went up approximately linearly; the normal displacement of the bullet obliquely penetrating into the UHMWPE target plate decreased slowly after reaching the peak, and the peak value of the normal penetration displacement decreased gradually with the increase of the angle of incidence, and the time to peak of the displacement shortened gradually. The damage area of the bulge on the back surface of the UHMWPE target plate after penetration decreased gradually with the increase of the angle of incidence. The research results can provide a theoretical reference for the application of UHMWPE laminates in the design of military bulletproof shelters and armor.

Имитационное моделирование работы рекуперативного пневмогидравлического дышла сцепного устройства автопоезда с функцией самовытаскивания

Based on the conducted exploratory research, the most significant factors were identified on which the change in
 transport costs spent by logging enterprises on the process of delivering timber to consumers by logging trucks depends.
 To reduce such costs, a promising design of the drawbar of the coupling device of a timber road train has been proposed,
 providing the effect of self-pulling of the road train, generating and storing the energy of the working fluid, with its
 subsequent use in technological hydraulic equipment. To simulate the movement of a timber road train equipped with the
 proposed drawbar of the coupling device and the operation of the drawbar separately in the modes of self-pulling, recovery
 and damping of dynamic loads, two computer programs have been developed. It has been established that with an increase
 in the depth of irregularities, self-pulling of a timber road train becomes more difficult, which leads to a deterioration in
 the efficiency of the self-pulling process. However, with an average depth of unevenness of the supporting surface of less
 than 0.3 m, the efficiency indicators of the self-retracting process are acceptable values: the self-retracting speed is more
 than 0.22 m/s, the amount of displacement per extension-reduction cycle of the drawbar of the coupling device is less than 0.12 m, consumed by the pneumohydraulic drawbar of the coupling device power less than 1.9 kW. Under very
 difficult road conditions – the average depth of irregularities is from 0.3 to 0.5 m – the self-pulling of the timber road
 train occurs, but the efficiency indicators decrease: the self-pulling speed decreases to 0.16 m/s, the movement increases
 to 0.17 m, power consumption increases to 3.1 kW. It was revealed that when the coefficient of viscous friction of the
 wheels of a logging road train against the supporting surface of a logging road changes over a wide range, the recuperative
 pneumohydraulic drawbar of the coupling device provides a fairly effective self-pulling with a self-pulling speed from
 0.17 to 2.3 m/s, a displacement (rollback) value from 0.09 to 0.16 m, power consumption from 1.5 to 2.2 kW.

Effects of different patterns of movement for correcting a deep curve of Spee with clear aligners on the anterior teeth: a finite element analysis

ObjectiveTo analyse the anterior teeth effects of clear aligners on five different patterns of mandibular molar movement and to define the most effective configuration to be implemented with clear aligners through finite element analysis.MethodsA three-dimensional mandibular model with a deep overbite in the mandible was constructed using cone beam computerized tomography (CBCT) data. The model included the mandibular dentition, mandibular periodontal ligaments, attachments, and aligners. Five models were created: (1) configuration A: second molar distalization (0.25 mm); (2) configuration B: second molar distalization (0.25 mm), first molar extrusion (0.15 mm); (3) configuration C: second molar distalization (0.25 mmm), first and second premolar extrusion(0.15 mm); (4) configuration D: second molar distalization (0.25 mm), first molar and first/second premolar extrusion(0.15 mm); and (5) configuration E: second molar distalization (0.25 mm), first molar and first/second premolar extrusion (0.15 mm), first molar and first/second premolar expansion (0.15 mm).ResultsIn all configurations, the anterior teeth exhibited labial tipping and the mandibular central incisor of configuration E showed the highest labial tipping. Configuration E demonstrated a relatively minor impact on mandibular molars distalization compared with configuration A. Configuration A showed the highest distal displacement value, and configuration E produced the lowest displacement value. Configuration E caused the highest periodontal ligament (PDL) pressure of the central and lateral incisors. The differences in the canines between configurations C and D,were not significant, and the stress distribution differed among the five groups.ConclusionsAll patterns utilizing clear aligners facilitated mandibular molar distalization. Extruding the premolars and second molar distalization at the same time had little impact on second molar distalization; When expansion and extrusion were simultaneously performed during the distalization of mandibular molars, our prime consideration was the alveolar bone on the labial side of the anterior teeth to prevent the occurrence of gingival recession, dehiscence, and fenestration. Due to the lack of consideration for periodontal tissues in this study, clinical protocols should be designed based on the periodontal status of the mandibular anterior teeth.

Optimization Analysis of Partition Wall Support Scheme of Multi-Arch Tunnel

With the fast progress of infrastructure projects, super-large cross-section projects are constantly emerging, and, therefore, engineering challenges and problems are increasing. Taking the triple-arch tunnel project in the turn-back line section of Santunbei Station in Urumqi Metro Line 1# as a case study, this research applied numerical simulation software Midas GTS/NX 2022 for the analysis of tunnel force and deformation in triple-arch cross-sections under different support forms of partition wall. Following the optimization of the support design of the mixed partition wall to a single straight wall, the following analytical results were obtained: surface settlement was decreased by 21.15% at the original cross-section; maximum values of principal stress and displacement of partition wall were decreased by 6.73 and 10.64%, respectively; and corresponding values for initial support structure were decreased by 21.47% and 54.74%, respectively. Meanwhile, combined with comparative analysis of engineering measurement and numerical simulation results, surface settlement and vault deformation were found to be similar to the optimized simulation results, which not only verified the reliability of simulation results but also ensured the safe and smooth construction of the project, greatly improving construction efficiency and saving construction time and cost.

Online optimal tuning of fuzzy PID controller using grey wolf optimizer for quarter car semi-active suspension system

In order to reduce vibration and increase ride comfort, this article utilizes a system of quarter-car suspension integrated with a Fuzzy PID controller. To build and improve the Fuzzy PID controller for the semi-active suspension system used in quarter cars, using a novel meta-heuristic technique known as Grey Wolf Optimizer (GWO). Here the magnetorheological damper (MR) fluid with the Fuzzy PID controller was examined to optimize using the GWO algorithm. With the GWO technique and the integral of time absolute error (IAE) as a fitness function, the three gain parameters of the Fuzzy PID controller – Kp, Ki, and Kd– have been optimally set. The suggested approach has additional advantages for the optimization of functions with three variables, including simplicity in implementation, quick convergence traits, and superior computational capabilities. This work is significant, to the best of the author’s knowledge there is no optimization method using GWO to online tune a Fuzzy PID controller for a semi-active suspension system. The optimal output parameters of the controller can be updated online in real-time by GWO. The performance of the proposed controller was examined by assessing the root mean square (RMS) values and peak-to-peak (PTP) values of body displacement and body acceleration under various road profiles. To ensure that the intelligent controller was of the highest caliber, an online test rig was constructed. Results from simulations and online experiments demonstrated that the Fuzzy GWO PID controller significantly improved ride comfort under a variety of road conditions when compared to the Fuzzy PID controller and passive suspension system.

Biomechanical evaluation of screw and cement placement strategies for treating medial uncontained tibial defects in total knee arthroplasty: A finite element analysis.

Total knee arthroplasty faces challenges in the management of medial uncontained tibial defects, affecting prosthesis stability and implant survival. The use of screws and bone cement is a preferred approach; however, optimal screw insertion techniques lack consensus in the existing literature. The present study aimed to address this gap by exploring optimal screw and cement placement strategies, focusing on their biomechanical implications. The present study conducted a finite element analysis using a knee prosthesis model with a defined uncontained tibial defect. Various parameters were systematically adjusted, including the number of screws (1, 2 or 3 screws), screw lengths (10, 18, 30 or 40 mm), lateral-medial screw positions (2, 4 or 6 mm laterally) and abduction rotation angles (0, 5, 10 or 15 degrees). These adjustments were made to evaluate their specific and combined impacts on the vertical displacement and abduction angles of the tibial tray. The results revealed that incorporating three-screw reinforcement markedly reduced vertical displacement, while the single screw in the middle position exhibited superior performance in preventing the deformation of abduction angles compared to scenarios with two screws at anterior and posterior positions without a middle screw. Longer screws and smaller abduction angles contributed to decreased movement of the tibial component. Furthermore, the lateral adjustment of the screw position led to an increase in vertical displacement values, reaching ~1.5% when shifted 6 mm laterally. On the whole, the finite element analysis in the present study suggests that, for the treatment of medial uncontained tibial defects, three-screw reinforcement is advantageous for larger defects. Longer screws and a smaller abduction angle are deemed favorable. Moreover, the results underscore the superiority of medial screw placement over lateral placement. It is imperative to note that further clinical validation is essential to corroborate the biomechanical implications observed herein.

Finite Element Analysis of the Influence of Implant Tilting and the Direction of Loading on the Displacement and Micromotion of Immediately Loaded Implants

ABSTRACT Objectives: To investigate the outcome of the loading direction and implant tilting on the micromotion and displacement of immediately placed implants with finite element analysis (FEA). Materials and Method: Eight blocks of synthetic bone were created. Eight screw-type implants were inserted, four axially and four slanted, each measuring 11 mm in length and 4.5 mm in diameter. The axial implants and the tilted implants were distally inclined by 30°. The top of the abutment was subjected to 180 N vertical and mesiodistal oblique (45° angle) loads, and the displacement of the abutment was measured. The abutment displacement and micromotion were estimated, and nonlinear finite element models simulating the in vitro experiment were built. In vitro studies and FEA data on abutment displacement were compared, and the reliability of the finite element model was assessed. Result: Under oblique stress, abutment displacement was larger than under axial loading, and it was also greater for tilted implants than for axial implants. The consistency of the in vitro and FEA data was satisfactory. Under vertical stress, the highest micromotion values in the axial and tilted implants were extremely near Conclusion: Under mesiodistal oblique stress, tilted implants may have a smaller maximum amount of micromotion than axial implants. The loading direction had a significant impact on the highest micromotion values. The abutment displacement values were not reflected in the maximum micromotion measurements.

3D numerical analysis of corner mechanically stabilized earth walls

ABSTRACT MSEW (Mechanically Stabilized Earth walls) has become a widely adopted and economical earth-retaining system. However, the current design standards primarily rely on a two-dimensional plane-strain approach, overlooking the critical 3D behavior and mechanisms associated with wall curves and corners. To address this gap, this research aims to enhance our comprehension of MSEW corner performance for right-angle (Sharp turns) and curved (Round off) walls by using 3D finite element modeling. A comparative study was conducted for MSEW in case of sharp turns and round off walls, in addition to examining the influence of the curve angle in the different cases with angles (internal curve angle) of 50 to 120 degrees. Based on results of comparing the right-angle wall and the curved angle (90º) wall, it is evident that the horizontal displacement of the right-angle wall is greater. For curved wall, it was observed that the value of horizontal displacement is minimal at the beginning of the curved wall and gradually increases until it reaches the maximum displacement at the mid of the curve in plan view. The geogrid strain for the right-angle wall is approximately 1.70 times of the curved wall (internal curved angle = 90°). Based on the results of difference angle of curved wall, it was concluded that the horizontal displacement values of the wall between internal curved angles 90 and 120 are quite close, but they differ significantly from 50 to 90. It was noted that, the maximum displacements for angles from 60 and 110 was occurred at approximately 0.38 H of the wall’s height from the base but, it equal to 0.50 H for angle 110 and 120. Finally, an equation of second degree can be deduced to illustrate the relationship between the maximum facing wall displacement and the wall height with the curved wall angle.

Biomechanical Evaluation of 2 Endoscopic Spine Surgery Methods for Treating Lumbar Disc Herniation: A Finite Element Study.

This study aimed to evaluate the effects of 2 endoscopic spine surgeries on the biomechanical properties of normal and osteoporotic spines. Based on computed tomography images of a healthy adult volunteer, 6 finite element models were created. After validating the normal intact model, a concentrated force of 400 N and a moment of 7.5 Nm were exerted on the upper surface of L3 to simulate 6 physiological activities of the spine. Five types of indices were used to assess the biomechanical properties of the 6 models, range of motion (ROM), maximum displacement value, intervertebral disc stress, maximum stress value, and articular protrusion stress, and by combining them with finite element stress cloud. In normal and osteoporotic spines, there was no meaningful change in ROM or disc stress in the 2 surgical models for the 6 motion states. Model N1 (osteoporotic percutaneous transforaminal endoscopic discectomy model) showed a decrease in maximum displacement value of 20.28% in right lateral bending. Model M2 (unilateral biportal endoscopic model) increased maximum displacement values of 16.88% and 17.82% during left and right lateral bending, respectively. The maximum stress value of L4-5 increased by 11.72% for model M2 during left rotation. In addition, using the same surgical approach, ROM, maximum displacement values, disc stress, and maximum stress values were more significant in the osteoporotic model than in the normal model. In both normal and osteoporotic spines, both surgical approaches were less disruptive to the physiologic structure of the spine. Furthermore, using the same endoscopic spine surgery, normal spine biomechanical properties are superior to osteoporotic spines.

Finite Element Analysis of Aluminum Based R22 Car Wheel Design Modification

The wheels are one of the main parts of the vehicle. To make car wheels, manufacturers must complete several stages. Especially in the design of the wheels. This study aims to determine the comparative value of three different types of wheels with the same material using aluminum type 6061-T6 (SS). We will test the three-wheel models, namely model 1, model 2, and model 3, with a force of 3000 N and a pressure of 800 N to compare their performance. This test uses Solidworks 2019 software with the finite electronic analysis (FEA) method. The results obtained are the value of Von Misses stress, resulting displacement, equivalent strain and its deformation, and factor of safety. The dimensions of the wheels are 22 inches. The results of the best Model 3 alloy wheel research indicate that the design process is easier. These wheels have a Von Misses stress value of 11.02 MPa with a resulting displacement value of 0.021 mm, an equivalent strain of 0.000096, a safety factor of 25, and a deformation value of 1. Based on these results, model 3 alloy wheels are safe.

Dynamic Response of Offshore Wind Turbine with a New Monopile Foundation under Different Lateral and Seismic Loadings

Using a monopile foundation due to a reliable and simple technology has a wide application in engineering structures. This paper investigates numerically the performance of an offshore wind turbine with a monopile foundation equipped with a restriction plate at a middle inside height of the monopile under the wind, wave, and seismic loadings. Different parameters, including wind velocity, wave period, wave height, soil characteristics, and combination of loadings, are considered in nonlinear finite element dynamic analyses. Results are given in terms of the distribution of displacement and bending moment over the turbine height and frequencies. The results reveal that by increasing the wind velocity, the responses of the tower increase, and the wind load acting on the hub has the most important effect on the turbine behavior rather than the wind load acting on the tower body. Furthermore, the values of maximum displacement and bending moment under wind and wave loading decrease with the increase of the shear strength of the soil, whereas the responses of the tower under earthquake loading increase. Generally, it is necessary to consider the effect of a combination of wind, wave, and earthquake loadings on the design of the turbine tower.

Farklı Duvar ve Harç Malzemeleri İle Üretilen Duvarların Mekanik Özelliklerinin Belirlenmesi

Walls produced using different masonry materials and mortars are among the structural elements that carry horizontal and vertical loads. In this context, the mechanical properties of walls produced with different wall and mortar materials have been investigated. In the production of wall samples, Harman Brick (HB), Masonry Brick (MB) and Bimsblok (BB) were chosen as the mesh material Reinforced Mortar (RM) and Polypropylene Fiber Added Mortar (PM) were used as binding materials in the construction of the walls produced in 900x900 mm dimensions. The volumetric mixing ratios of the mortar used were prepared as sand:cement:lime=6:1:1, according to the TSE 2510 standard. The bricked wall samples were subjected to diagonal loading tests after being kept in the laboratory environment for 28 days. Flexural and compressive strengths of the mortars used in wall building, displacement values of the walls, shear strength, rigidity modulus, energy absorption capacity and collapse patterns of the walls were determined. The graphs of the displacement values obtained by examining the behaviors observed in the test samples and the cracks formed were interpreted. It was observed that the shear strength of the walls built using PM was higher than the shear strength of the walls built using RM. The energy absorption capacity was highest in the fibrous specimen laid with masonry bricks. The average vertical load value of the wall specimens built with fibrous mortar, which is the BB of the masonry material, was 30% higher than the specimens built with non-fiber mortar.

Numerical simulation of the bentonite-bonded sand mould compaction process using micro-mechanical parameter relationships

ABSTRACT Commercial software packages for FEM analysis have been used to numerically simulate the behaviour of the complex systems of bentonite-bonded sand mould under pressure and subjected to stress distributions and to predict their performance. The Drucker-Prager model and the Mohr-Coulomb model are two well-known mathematical models used to describe the plastic non-linear behaviour of the soil. Conducting direct shear tests on varying densities of sand can provide the individual parameters necessary for the simulation of the moulding process. A new approach is based on making relationships between micro-mechanical parameters and changes in sand density during the compaction process. COMSOL Multiphysics is a popular software tool used to implement FEM simulations. The steps involved drawing geometry, inserting material properties, mesh generation and time-dependent density, and solving the model. The boundary conditions depend on the particular problem being analysed, which defines the external forces and constraints acting on the structure. The use of a coarse mesh and stationary study may be a computationally efficient approach for the evaluation of the compaction process of green sand. The study found that the maximum displacement value is 6.1*10−3 mm, the maximum volumetric strain value is 8.88*10−5, and the von Mises stress is 4.14*103 N/m2.

Hybrid fibre reinforced recycled aggregate concrete: dynamic mechanical properties and durability

Research into recycled aggregate concrete (RAC) has been on the rise as there is a need to preserve natural resources and promote sustainable infrastructure practices. In our previous study, a new hybrid-fibre reinforced recycled aggregate concrete (FRRAC) with micro basalt fibre (BF) and recycled macro polypropylene fibre (PF) was developed and its physical and mechanical properties were investigated. As a continuous work, this study investigated the dynamic mechanical properties and durability of the developed FRRAC. Dynamic compressive and splitting tensile strength tests were undertaken using a Ø 100 mm split Hopkinson pressure bar (SHPB) system. The failure processes and failure modes of RAC and FRRAC specimens under different strain rates were recorded using a high-speed camera. For dynamic compressive strength, the stress-strain curves, dynamic increase factor for compressive strength (DIFf’c) and energy absorption capacities of RAC and FRRAC were evaluated and compared in the strain rate range from around 27.9 s-1 to 138.0 s-1. The stress-time histories, crack-opening displacement values and dynamic increase factor for splitting tensile strength (DIFfst) at the strain rates of around 3.03 s-1 to 8.17 s-1 of the two materials were obtained and compared. The test results indicated that RAC specimens were slightly more strain rate sensitive than natural aggregate concrete (NAC) under dynamic compression and splitting tension. On the other hand, FRRAC specimens showed similar strain rate sensitivity as their counterparts with no fibres under dynamic compression but showed lower DIFfst values with increasing strain rate under splitting tension. Empirical formulae for DIFf’c, DIFfst and energy absorption capacities against strain rates were proposed. In addition, the durability performance was assessed by examining the water absorption, volume of permeable voids (VPV), water sorptivity and chloride ion penetration resistance. Durability test results indicated that RAC and FRRAC in this study are suitable for structural applications.

Horizontal displacement at the top of the building with frame and shear walls structures according to TCVN 2737:2023

When designing the structure of a high-rise building, it is important to consider not only the load-bearing capacity of the entire building but also the issue of limiting horizontal displacement at the top of the building. In this study, the author used Etabs software to analyze and compare the horizontal displacement at the top of a building. The study focused on two different types of structural system: frame system (consisting of columns, beams, and floors) and shear walls (which consists just of reinforced concrete walls). The analysis was conducted in accordance with Vietnamese standards on loads and impacts, specifically TCVN2737:2023. The wind loads were applied to the geometric center of the structure. Research results suggest the impact of horizontal displacement at the top of high-rise buildings is significant. Additionally, it has been observed that the shear walls system shows an increased horizontal displacement value compared to the frame system.