Initial Force Research Articles

Evaluating construction parameters of HB and CD methods for super large section tunnel: a case study

The double sidewall guide pit and centre cross diagram (CRD) methods are often used for the construction of large-section tunnels through water-rich fault fracture zones due to their long construction time and high construction cost. To shorten the construction period and save costs, the top heading and benching method (HB) and centre diaphragm (CD) can be chosen for construction. The construction parameters of the step and CD methods are optimized to ensure the surrounding rock stability and tunnel safety. By relying on the Tongzi Tunnel, we simulate the excavation of different step heights in the construction of the top heading and benching method (HB) and CD methods through numerical simulation, the laws of tunnel vault settlement, and changes in the surrounding rock stress, initial support axial force, bending moment and safety factor. The study shows that as the height of the upper step increases, the settlement of the vault and the convergence of the periphery increase, the initial support safety factor decreases, and the plastic zone of the surrounding rock increases at 30 m from the target face. The step height for the top heading and benching method (HB) of construction is optimized as follows. The ratios of the upper, middle and lower step heights are 0.45H, 0.35H and 0.2H, respectively. The CD method construction step height is optimized to the left (right) upper and left (right) lower step height ratios of 0.5H and 0.5H, respectively.

Moisture dependent postharvest physical and textural characteristics of brown sesame seed (var. TMV-4)

Physical and textural characteristics are important in design and manufacturing of harvest and post harvest machines. Some postharvest physical and textural characteristics of brown sesame seed (var. TMV-4) were determined as a function of moisture content in the range of 4.3 per cent to 20 per cent (d.b). The axial dimensions, geometric mean diameter, surface area, volume, sphericity and aspect ratio were found to be increasing linearly for all studied moisture levels. Furthermore, the thousand seed mass, true density, porosity and the angle of repose also increased linearly whereas, bulk density decreased linearly with the increase of moisture content under study. The results showed that the static coefficient of friction on four different surfaces of plywood, mild steel, galvanized iron and glass also increased linearly for all level of moisture. The initial cracking force, average rupture force and average rupture energy decreased linearly with increased moisture content of 4.3 to 20 per cent (d.b.).

Predicting Multiple Numerical Solutions to the Duffing Equation Using Machine Learning

This study addresses the problem of predicting convergence outcomes in the Duffing equation, a nonlinear second-order differential equation. The Duffing equation exhibits intriguing behavior in both undamped free vibration and forced vibration with damping, making it a subject of significant interest. In undamped free vibration, the convergence result oscillates randomly between 1 and −1, contingent upon initial conditions. For forced vibration with damping, multiple variables, including initial conditions and external forces, influence the vibration patterns, leading to diverse outcomes. To tackle this complex problem, we employ the fourth-order Runge–Kutta method to gather convergence results for both scenarios. Our approach leverages machine learning techniques, specifically the Long Short-Term Memory (LSTM) model and the LSTM-Neural Network (LSTM-NN) hybrid model. The LSTM-NN model, featuring additional hidden layers of neurons, offers enhanced predictive capabilities, achieving an impressive 98% accuracy on binary datasets. However, when predicting multiple solutions, the traditional LSTM method excels. The research encompasses three critical stages: data preprocessing, model training, and verification. Our findings demonstrate that while the LSTM-NN model performs exceptionally well in predicting binary outcomes, the LSTM model surpasses it in predicting multiple solutions.

Energy absorption characteristics of thin-walled tube filled with liquid suspension of hollow glass microspheres under axial crushing

The deviation between the high initial peak force and low mean crushing force of thin-walled tubes has significantly limited its energy absorption efficiency. To tackle this challenge, a liquid suspension of hollow glass microsphere (SHGM) is employed as a new type of filling material. The axial crushing behavior of SHGM-filled tubes is evaluated by a series of quasi-static compression and dynamic drop weight impact tests. Results show that the specific energy absorption of the composite tube is increased more than 40 %. The energy absorption efficiency of SHGM-filled tube is increased to 0.65–0.70 compared to that of empty tube (0.37–0.43). This promoted energy absorption performance of the composite tube is due to the much-enhanced SHGM liquid filler-tube wall interaction, which is validated from the increased strengthening coefficient of 4.0. This enhanced filler-tube wall interaction is visualized by using 3D digital image correlation technique. These results demonstrate that the SHGM is a superior filling material for thin-walled structures and facilitate the design of next generation lightweight composite structures for energy absorption purposes.

The design of circular tubes with stepped varying thicknesses and their synergistic multi-tube combination

A stepped wall circular tube with varying thickness (STVT) and its multi-tube synergistic combination energy absorption structure were developed to address the shortcomings of the high initial peak force of thin-walled metal tubes and the significant load fluctuation of conventional multi-tube combination structures. The STVT was designed with different thickness variations, and its crashworthiness was evaluated numerically and experimentally. An analysis was done on the influences of various characteristics, such as the number of steps and thickness variation, on the crashworthiness of STVTs. Research shows that the STVT with three and four steps has improved crashworthiness. The phase of the curve is significantly influenced by the initial thickness, and for each 0.6 mm difference in step thickness, the peak phase shifts by about 5.5%. In comparison to the combination of four equal-thickness tubes of the same mass, the optimal combination structure optimizes smoothness by 10.67%, energy absorption by 19.52%, crushing force efficiency by 15.30%, and initial crushing force by 20.70%.

The universe generated by the explosion of the primordial cosmic vacuum!

Over all its epochs mankind always has put the fundamental question: When and why at all did the universe start its existence? Most cosmologists univocally do answer this question with the standard dogmatic answer: By the Big-Bang! - namely by the initial explosion of an extremely concentrated world matter system! This standard paradigm of a general and global explosion creating this world obviously appears to be highly suggestive, though such an explosive event unexpectedly turns out to be extremely hard to understand on purely physical grounds. This is because it is extremely hard to explain which pressures might be responsible to drive the initially highly compacted cosmic matter apart. The somewhat naive idea that the required explosion forces in view of the extremely high temperatures and the extreme highly compacted primordial cosmic matter, are due to extreme initial pressure forces does not solve the problem, because relativistically hot matter will be just an additional source of gravity, hence just contrary to the expectations impedes matter to fly apart. It can, however, be shown that the expected explosive BB- event can only physically occur, if the required pressure is not established by the temperature of gravitating matter, but by the cosmic vacuum. In fact we show that without this cosmic vacuuum pressure, the so-called Big-Bang never could have happened, even though vacuum pressure up to the present days of cosmology, still may be a rather speculative subject. In the following article we shall demonstrate that with a revised understanding of this highly speculative quantity one can explain the present universe as an explosion of the primordial cosmic vacuum followed by a succesive materialisation of this vacuum into cosmic matter at the ongoing cosmic expansion.

Multi-Objective Optimization of Square Corrugation Multilayer Nested Structures

Thin-walled structures, when used for high-speed railways, can effectively mitigate the irreversible destruction when a malfunction occurs. Nested thin-walled tubes, as energy-absorbing structures, possess excellent specific energy absorption (SEA) and crushing force efficiency (CFE). This paper conducts multi-objective optimization by focusing on a square corrugation nested structure with a double octagon inner wall, namely SCOD, to ameliorate the crashworthiness of the nested structure. The finite element model of the SCOD is constructed and validated by test data. A set of experimental design points with good spatial distribution are obtained using the optimal Latin hypercube (LHC) method. The polynomial response surface (PRS) method was applied to establish the fitting relationship between design variables and optimization objectives, and validation is accomplished. The DCNSGA-III algorithm is employed for optimization, resulting in a Pareto alternative solution set with good population diversity and convergence. In addition, to observe the optimized performance, a set of optimal solutions considering a single objective value is derived, and a comprehensive optimal solution is obtained by applying the minimum distance selection method (TMDSM). Finally, the proposed optimized system is analyzed and validated. According to the alternative reference solutions, the initial peak force (IPCF) reduces by 53.75% and CFE increases by 8.7%. This paper provides some reference for the optimization design in practical engineering.

During Postless Hip Arthroscopy, Male Patients, High Body Mass Index, Low Beighton Scores, and Limited Range of Motion Require High Traction Force

To determine the effects of demographic and anatomic factors on traction force required during postless hip arthroscopy. A prospectively collected database was retrospectively analyzed on patients undergoing hip arthroscopy by the senior author, including patient sex, age, body mass index (BMI), Beighton Hypermobility Score, hip range of motion in clinic and under anesthesia, hip dysplasia, acetabular version, and femoral version. All patients underwent postless hip arthroscopy under general anesthesia. At the initiation of hip arthroscopy, the traction force required to distract the hip joint was measured before and following interportal capsulotomy. Multiple regression analysis was performed to determine the effects of demographic and anatomic factors on measured distraction force. In total, 352 hips (114 male, 238 female) were included with a mean age of 32.6 years and a mean BMI of 24.1 kg/m2. Mean initial traction force was 109 lbs and decreased to 94.3 lbs following capsulotomy (P < .0001). The starting traction force was significantly greater in male patients (P < .001), patients with a lack of hypermobility (Beighton Hypermobility Score of 0-2) (P= .026), and in patients with lower abduction (P < .001), lower internal rotation (P= .002), and lower external rotation (P= .012) on multiple regression analysis. When performing a subanalysis divided by sex, male patients with elevated BMI required significantly greater starting traction force (P= .014). Lateral center edge angle, sourcil angle, and the presence of hip dysplasia did not demonstrate a significant correlation with traction force. Male patients, patients with reduced preoperative hip range of motion, patients with a lack of joint hypermobility, and male patients with an elevated BMI require greater initial traction force during postless hip arthroscopy. Level IV, retrospective case series.

Characterization and Modeling of Ply/Tool and Ply/Ply Slippage Phenomena of Unidirectional Polycarbonate CF Tapes.

Thermoplastic tapes are commonly processed by the rapid and efficient stamp forming process. During this forming process, the individual unidirectional tapes of the composite stack move relative to each other and relative to the surface of the tool while being in contact with the corresponding counterpart. As a result, the material exhibits a certain resistance against this movement, which is generally dependent on velocity, normal pressure, and temperature. Therefore, this work investigates the ply/tool and ply/ply slippage of unidirectional, carbon fiber reinforced polycarbonate tapes and provides an alternative implementation of the experimentally observed slippage using cohesive zone modeling. The backbone of the modeling approach is an experimental data set obtained from pull-through experiments. In comparison to common slippage or friction theories, the force plateau of thermoplastic UD tapes at elevated temperatures is observed after an initial force peak has been overcome. For both configurations, ply/tool and ply/ply, a reduction of the initial force peak was observed for increasing temperature. Furthermore, the resulting plateau force value is at least 36% higher in the ply/ply configuration compared to the ply/tool configuration at 200 °C. The derived cohesive zone model allows for accurate modeling of the initial force peak and the plateau.

Lubrication analysis of the piston ring for the two-stroke marine diesel engine based on modified radial tension

As the piston ring is inserted into the bore, it is forced against the liner by radial tension, thereby creating a seal. Radial tension not only affects the piston ring’s seal, but also significantly influences its tribological properties. To investigate the effect of non-uniform radial tension of piston ring on the lubrication properties, a contact finite element model of piston ring and cylinder liner tribo-pairs is constructed in this study. The contact pressure distribution between the tribo-pairs is determined based on this model. The obtained pressure is then regarded as the non-uniform radial tension of the ring, which is fitted to a formula. The formula is validated in two ways. Firstly, its generality is verified by simulating several different piston rings using the contact model and comparing their results with the formula. Second, a test rig was designed and set up to measure the piston ring’s circumferential tension. To verify the formula’s accuracy, an equivalent principle model of distributed pressure and concentrated force was proposed. This formula is used as an initial force to modify the piston ring mixed lubrication model. Based on this model, the lubrication performance of the piston ring with uniform radial tension and non-uniform radial tension into consideration is investigated. The findings demonstrate that the piston ring radial tension is of significance to its lubrication performance and can be modified to lessen local friction and wear issues, particularly those related to the piston ring gap, and thus improve the dependability of the piston ring.

Antimicrobial and mechanical assessment of cellulose-based thermoformable material for invisible dental braces with natural essential oils protecting from biofilm formation

Controlling biofilm formation in the oral cavity during orthodontic treatments is crucial. Therefore, antimicrobial surfaces for invisible dental appliances are of interest to both therapists and patients. Here we present a cellulose-based thermoformable material used for invisible braces that can be loaded with essential oils (EOs) having antibacterial and antifungal properties. We hypothesize that this material can absorb and release EOs, thus providing an antimicrobial effect without compromising the safety and mechanical properties necessary for dental invisible braces. Conventional microbiology and isothermal microcalorimetry analyses revealed that the thermoformable material loaded with essential oils significantly delayed the biofilm formation of oral streptococci (S. mutans and S. mitis) under static conditions (p < 0.05) and while simulating saliva flow (p < 0.05). In addition, cytotoxicity tests (ISO 10993-5), revealed that the loaded material is well tolerated by human gingival fibroblasts. Finally, the loading with antibacterial agents did not significantly alter the mechanical properties and stability of the material (initial force (p = 0.916); initial stress (p = 0.465)). Compared to gold-standard clear aligner materials, this material offers a reliable transmission of forces for orthodontic treatments. Moreover, this approach exhibits the potential for acting as an oral drug delivery platform for multiple compounds.

Thermally-induced vibration analysis of tensegrity modules during space deployment using dynamic stiffness method

Tensegrity is an ideal structural form for the modular assembly of ultra-large spacecraft. Understanding the dynamics of tensegrity modules during deployment under thermal effects is crucial for successful space deployment. In this paper, a space deployment dynamics model for tensegrity modules that incorporates dynamic stiffening and space thermal effects is developed using a rotating Bernoulli–Euler beam. The dynamic stiffness method is introduced to obtain numerically accurate solutions for the system’s modal characteristics and dynamic response under space thermal effects. The deviation between the fundamental frequency and the finite element solution is within 1‰, and the maximum displacement deviation is 3%, confirming the accuracy of our method. Parametric analysis reveals that as the deployment speed increases, the frequency of the tensegrity modules' compression bars gradually increases, and an exchange between transverse and longitudinal modes occurs. Moreover, increasing the initial force and the angle of heat flow incidence leads to higher response amplitudes in the compression bars of tensegrity modules. This analysis reveals the dynamic evolution of tensegrity module space deployment under thermal effects.

The Effect of Different Soft Drinks on the Force Degradation of Conventional and Memory Orthodontic Elastic Chains: An In-Vitro Study.

Objectives: The aim of this study was to assess how different soft drinks affect the deterioration of conventional and memory orthodontic elastomeric chains. Materials and Methods: We used 500 five-loop segments of elastomeric chains, which were divided into two equal groups of conventional and memory chains. The samples were kept in artificial saliva during the study period. Each group was further divided into 5 subgroups consisting of artificial saliva (controls), Coca-Cola®, non-alcoholic beer (ISTAK®), and carbonated and non-carbonated yoghurt-based drinks (Alis®). Treatment with the soft drinks consisted of immersion in the test liquids twice a day for 3 minutes each time. Force measurements were taken on days 1, 7, 14, 21, and 28. Data were analyzed using One- and three-way ANOVA tests, and independent t-test, with a significance level of 5%. Results: The mean initial force for the conventional and memory elastomeric chains was 3.34±0.112N and 2.49±0.209N, respectively. Conventional chains showed significantly greater degradation than memory chains (P<0.01). Soft drinks had a significant impact on force degradation for both types of chains at all time points (P<0.01). Coca-Cola® had the highest level of force degradation, while non-carbonated yoghurt-based drinks had the lowest (P<0.01). Conclusion: Based on the findings of this study, it is recommended that orthodontic patients choose non-carbonated yoghurt-based drinks during their treatment. Memory elastomeric chains may be more suitable for patients who consume large amounts of carbonated soft drinks, due to their lower amount of force degradation compared to conventional chains.

Experimental and theoretical investigations of post-tensioned precast reinforced concrete bridge pier with external replaceable energy dissipaters

This study presents a post-tensioned (PT) precast reinforced-concrete bridge pier with external replaceable energy dissipaters (PRCB-EREDs). The EREDs provide both bending resistance and energy dissipation (ED) capacity, and the unbonded PT strands enable prefabricated construction and self-centering capabilities. This study introduces the construction, assembly process, and post-earthquake repair technology of the PRCB-EREDs. Subsequently, parametric quasi-static tests were performed by altering parameters, such as the initial PT force and the size of core energy dissipation steel plate in the ERED (ERED-CEDP). The test results indicated that the precast pier column remained essentially elastic, with damage localized within the ERED-CEDP, exhibiting good deformation and ED capabilities. The hysteresis curve of the specimen was full and stable, and the curves before and after repair were essentially identical, confirming the feasibility of the repair. With an increase in the initial PT force, both the stiffness and bearing capacity were improved, and better self-restoration effects were achieved. For test conditions with the same ERED-CEDP thicknesses but different initial PT forces, the ED capacities were almost the same. Finally, the load-resisting mechanism of the PRCB-ERED piers was analyzed and theoretical model of hysteretic behavior was proposed and verified.

Initial retention force of three attachment systems for implant retained-mandibular overdentures: An in vitro study.

To evaluate and compare the initial retention force of three resilient unsplinted attachment systems for implant-retained mandibular overdentures: two cylindrical attachment systems (Locator R-Tx® and Novaloc®), and one ball attachment system (Ball System). For each attachment system, initial retention is measured as the average of the maximal dislodging forces during 10 insertion-removal cycles. For the Ball System, three activation degrees of the matrix are included versus four and six color-coded retention devices for the Locator R-Tx® and the Novaloc®, respectively, to represent the complete regular retention devices panel. For each retention device or activation degree, eight samples are tested. The initial retention range is similar between the Ball System (7.7 ± 3.4 N - 19.9 ± 4.6 N) and the Novaloc® (2.0 ± 0.5 N - 18.9 ± 1.4 N) and broader for the Locator R-Tx® (3.3 ± 5.0 N - 60.2 ± 6.0 N). In each attachment system, the initial retention of each retention device is significantly different from the others, except for the two most retentive Novaloc® ones. Retention devices were also classified according to their initial retention (low, medium, and maximum). In each retention group, the Novaloc® and the Ball System provided similar retention values lower than the Locator R-Tx®. Most of the retention devices tested provided an initial retention force of over 5 N for all three attachment systems. The Locator R-Tx® had the most comprehensive range, and the Novaloc® seemed to provide the most reproducible values, unlike the Ball System due to the activation required by the operator.

Seismic behavior of cable-stayed bridges under strong ground motions

Seismic behavior analysis of the long-span cable-stayed bridge is a complex process involving different uncertainties. This paper performs a sensitivity analysis of cable-stayed bridges using the finite element method on Midas/Civil. They include different types of ground motions scaled to different peak ground acceleration (PGA) levels, the effect of the multi-support excitations due to time-lag propagation or nonsynchronous excitations, and the effect of the angle of the incidence of the earthquake is determined. To evaluate the optimum initial cable prestress forces in cables unknown load factors method is used. The response quantities of interest include the displacement of the tower and deck, variation in prestress force in cables, torsional in the deck, shear force, and bending moment at the supports. Results show that the effect of the PGA variation and angle of incidence of the earthquake is moderate. In contrast, the synchronous and nonsynchronous seismic excitation effect on the response quantities is significant.

The Certification Matters: A Comparative Performance Analysis of Combat Application Tourniquets versus Non-Certified CAT Look-Alike Tourniquets.

The Stop the Bleed campaign provided civilians with tourniquet application training and increased the demand for tourniquets among the general population, which led to the development of new commercially available devices. However, most widely available tourniquets have not undergone testing by regulatory bodies and their efficacy remains unknown. This study aimed to compare the efficacy and performance of Combat Application Tourniquets (CAT) versus uncertified tourniquets. This study compared 25 CAT with 50 commercially available "look-alike" tourniquets (LA-TQ) resembling the CAT. The CAT and the LA-TQ were compared for cost, size, and tested during one-hour and six-hour applications on a manikin's leg. The outcomes were force applied, force variation during the application, and tourniquet rupture rate. The LA-TQ were cheaper (US$6.07 versus US$27.19), shorter, and had higher inter-device variability than the CAT (90.1 [SE = 0.5] cm versus 94.5 [SE = 0.1] cm; P <.001). The CAT applied a significantly greater force during the initial application when compared to the LA-TQ (65 [SE = 3] N versus 14 [SE = 1] N; P <.001). While the initial application force was maintained for up to six hours in both groups, the CAT group applied an increased force during one-hour applications (group effect: F [1,73] = 105.65; P <.001) and during six-hour applications (group effect: F [1,12] = 9.79; P = .009). The rupture rate differed between the CAT and the LA-TQ (0% versus 4%). The LA-TQ applied a significantly lower force and had a higher rupture rate compared to the CAT, potentially affecting tourniquet performance in the context of public bleeding control. These findings warrant increased layperson education within the framework of the Stop the Bleed campaign and further investigations on the effectiveness of uncertified devices in real-world applications.

An experimental and numerical approach for optimization of internal and external corrugations with various geometries in cylindrical thin-walled concertina energy absorbers under quasi-static axial load

Thin-walled tubes have been extensively used as energy absorbers in many engineering structures that are under dynamic or quasi-static loads. In this article, the effect of corrugation and its geometry on the collapse characteristics of aluminum concertina tubes under quasi-static axial load is investigated both experimentally and numerically. The numerical simulations were performed with the use of LS-Dyna commercial software. Then, several chosen samples were tested experimentally to verify the results of the simulation. Forty different samples with four different corrugation geometries including singly isosceles triangular corrugation, continual isosceles triangular corrugation, continual scalene triangular corrugation, and continual semi-circular corrugation, and each with 10 different size dimensions were simulated. Among all of these simulations, six of them, each with two replicates were subjected to experimental tests. Experimental examples are aluminum cylindrical thin-walled tubes with the same thickness, height, and diameter that corrugations with different geometries are applied to them by the use of the cold rolling method. Finally, to describe the findings in more theoretical terms, a comparison between our obtained results and earlier theoretical investigations is made. The results show a significant influence of corrugations application on the improvement of the collapse characteristics of the cylindrical tubes so that the collapse style of intact tubes can be controlled by applying corrugations. The results show that by increasing the amplitude and number of corrugations, the absorbed energy, and the initial maximum force decrease. It is also found that among the different corrugation geometries, the corrugations with singly isosceles triangular geometry have the highest energy absorption as well as the lowest initial maximum force.

Dynamical system of a time-delayed ϕ6-Van der Pol oscillator: a non-perturbative approach

A remarkable example of how to quantitatively explain the nonlinear performance of many phenomena in physics and engineering is the Van der Pol oscillator. Therefore, the current paper examines the stability analysis of the dynamics of ϕ6-Van der Pol oscillator (PHI6) exposed to exterior excitation in light of its motivated applications in science and engineering. The emphasis in many examinations has shifted to time-delayed technology, yet the topic of this study is still quite significant. A non-perturbative technique is employed to obtain some improvement and preparation for the system under examination. This new methodology yields an equivalent linear differential equation to the exciting nonlinear one. Applying a numerical approach, the analytical solution is validated by this approach. This novel approach seems to be impressive and promising and can be employed in various classes of nonlinear dynamical systems. In various graphs, the time histories of the obtained results, their varied zones of stability, and their polar representations are shown for a range of natural frequencies and other influencing factor values. Concerning the approximate solution, in the case of the presence/absence of time delay, the numerical approach shows excellent accuracy. It is found that as damping and natural frequency parameters increase, the solution approaches stability more quickly. Additionally, the phase plane is more positively impacted by the initial amplitude, external force, damping, and natural frequency characteristics than the other parameters. To demonstrate how the initial amplitude, natural frequency, and cubic nonlinear factors directly affect the periodicity of the resulting solution, many polar forms of the corresponding equation have been displayed. Furthermore, the stable configuration of the analogous equation is shown in the absence of the stimulated force.

Crashworthiness of bionic tree-shaped hexagonal hierarchical gradient structures under oblique crushing conditions

To improve the energy absorption characteristics of thin-walled structures under oblique loads, a new hexagon hierarchical gradient structure (HHGS) was designed in this work, which was inspired by the fractal structure of tree gradient in nature. The crashworthiness of the structure under oblique loads was systematically studied by numerical simulation method. The force-displacement curve of this structure under oblique loads is different from that of conventional thin-walled tubes under axial loads. Crashworthiness comparisons show that gradient structure can significantly reduce initial peak forces and maintain good deformation patterns and energy absorption advantages compared to other structures under oblique loads, at 15° load, the specific energy absorption of the third-order structure was increased by 59.20% at the highest level, at the same time, the initial peak force was reduced by 94.23%. At 30° load, the specific energy absorption of the third-order structure was increased by 32.30% and the initial peak force was reduced by 84.45%.