Reduction In Force Research Articles

Optimization of Ultrasonic-Assisted Incremental Sheet Forming.

Implementing the ultrasonic vibration-assisted incremental sheet-forming (UISF) process has been proven to significantly reduce the forming force, improve the surface quality, and enhance the accuracy of the sheet-forming process. However, such effectiveness has primarily focused on easily deformable materials (such as AA1050 and AA1060 aluminum alloys) and small step-down sizes (from 0.3 mm to 0.5 mm). To further enhance the process, it is crucial to study larger step-down sizes and harder materials. In this study, a series of UISF experiments were conducted, with step-down sizes ranging from 0.5 mm to 1.5 mm and feed rates ranging from 200 mm/min to 1200 mm/min. The influence of ultrasonic vibration on the effectiveness of force reduction and the optimal operation parameters was experimentally tested. Forming aluminum alloy AA5052, a difficult-to-deform material with two thicknesses of 0.5 mm and 1.0 mm, indicates that the axial force Fz and the tool movement resistance force Fy tend to decrease significantly with ultrasonic vibration assistance. Optimal equations for force reduction Fz and Fy have been developed for plate thickness based on the step-down size and feed rate. The optimal results show that for 1.0 mm thickness, reductions in Fz and Fy can reach 58.73% and 69.17%, respectively, and that of 64.17% and 71.98%, respectively, for 0.5 mm thickness.

Forensic Analysis on Damage of a Cable-Stayed Bridge without Backstays Using BIM Information

Serious cracks were found in the pylon of a cable-stayed bridge without backstays. Based on forensic damage investigation, this paper uses the finite element (FE) method incorporating Building Information Modeling (BIM) to analyze the causes of cracking. The BIM model is established based on the survey of design, construction, and service information of the bridge. Then, FE analysis is conducted using BIM information. Finally, the causes of cracking in different regions of the pylon are explained in detail. The results show that the FE simulation agrees well with the inspected distribution of cracks, and the causes of cracks are closely related to the pylon construction process. The main cause of the cracks is the shrinkage difference between concrete segments of different ages. The anchorage effect of stayed cables also causes inclined cracks perpendicular to the cable direction. The combination of temperature load and concrete shrinkage results in cracks at the root of the pylon, and the reduction in cable forces exacerbates the cracking.

Experimental evaluation and optimization of parameters affecting delamination, geometrical tolerance and surface roughness in ultrasonic drilling of 3D-Printed PLA thermoplastic

Ultrasonic drilling is a suitable process to enhance the generated surfaces by additive manufacturing. In this study, polylactic acid was selected as the workpiece. The examination parameters were thrust force, delamination, geometrical tolerance, chip adhesion, hole wall morphology and surface roughness. It was explained that the harmonic movement of drill bit in ultrasonic drilling reduced thrust force, delamination, circularity, cylindricality and surface roughness up to 14.5%, 3.7%, 44%, 38%, 20% respectively and removed chip adhesion. Furthermore, number of end-mill flutes was examined and observed that 4-flutes compared to 2-flutes induced reduction in thrust force, delamination, circularity, cylindricality and surface roughness up to 15.2%, 2%, 7.5%, 18.9%, 12.5% respectively. Besides, analysis of variance was established to determine the significant parameters. Finally, non-dominated sorting genetic algorithm-II technique was implemented in order to carry out multi-response optimization.

Effect of thermomechanical ageing on force transmission by orthodontic aligners made of different thermoformed materials: An experimental study.

Investigating the impact of thermal and mechanical loading on the force generation of orthodontic aligners made from various thermoplastic materials and different compositions. Five distinct materials were utilized including, three multi-layer (Zendura FLX, Zendura VIVA, CA Pro) and two single-layer (Zendura A and Duran). A total of 50 thermoformed aligners (n = 10) underwent a 48-hour ageing protocol, which involved mechanical loading resulting from a 0.2 mm facial malalignment of the upper right central incisor (Tooth 11) and thermal ageing through storage in warm distilled water at 37°C. The force exerted on Tooth 11 of a resin model was measured both before and after ageing using pressure-sensitive films and a biomechanical setup. Before ageing, pressure-sensitive films recorded normal contact forces ranging from 83.1 to 149.7 N, while the biomechanical setup measured resultant forces ranging from 0.1 to 0.5 N, with lingual forces exceeding facial forces. Multi-layer materials exhibited lower force magnitudes compared to single-layer materials. After ageing, a significant reduction in force was observed, with some materials experiencing up to a 50% decrease. Notably, multi-layer materials, especially Zendura VIVA, exhibited lower force decay. The force generated by aligners is influenced by both the aligner material and the direction of movement. Multi-layer materials exhibit superior performance compared to single-layer materials, primarily because of their lower initial force, which enhances patient comfort, and their capability to maintain consistent force application even after undergoing ageing.

The influence of uneven placement of mini dental implants on retention form of lower complete over denture: An in vitro study

Objectives: This in vitro study aimed to evaluate the effect of placing two mini-dental implant (MDI) at different heights on the retention form of the lower over denture (OD). Materials and Methods: Sixteen acrylic mandibular blocks and their corresponding ODs were prepared and divided into four groups (four sets per group) to represent an atrophic mandibular ridge with two MDIs placed parallel to each other at inter-implant heights (IHs) of 0.0, 1.5, 3.0, and 4.5 mm. The OD blocks were mounted on a manual pulling stand and pulled vertically 12 times to measure the peak tension load (N). The data were analyzed using one-way analysis of variance (ANOVA), and the differences between the means were compared (P < 0.05). Results: One-way ANOVA showed a statistically significant effect of IH on the retention force of the OD blocks (P < 0.05). The mean retention force (N) for evenly placed MDIs was as follows: 32.2 ± 0.95, 1.5 mm IH: 30.1 ± 0.56, 3.0 mm IH: 26.1 ± 0.71, and 4.5 mm IH: 27.4 ± 0.90. Conclusion: The retention force of the OD blocks was significantly affected by the vertical inter-implant distance. A significant reduction in the mean retention force was observed for ODs retained by MDIs placed at an IH >1.5 mm.

Optimal untwisting of the orbital bandeau in unicoronal craniosynostosis correction: A finite element analysis

BackgroundSurgical correction of unicoronal craniosynostosis (UCS) is highly complex due to its asymmetric appearance. Although fronto-orbital advancement (FOA) is a versatile technique for craniosynostosis correction, harmonization of the orbital bandeau in UCS is difficult to predict. This study evaluates the biomechanics of the orbital bandeau using different patterns and varying characteristics of inner cortical bone layer osteotomies in a finite element (FE) analysis. MethodAn FE model was created using the computed tomography (CT) scan of a 6.5-month-old male infant with a right-sided UCS. The unaffected side of the orbital bandeau was virtually mirrored, and anatomical correction of the orbital bandeau was simulated. Different combinations of osteotomy patterns, numbers, depths, and widths were examined (n = 48) and compared to an uncut model. ResultsReaction forces and maximum stress values differed significantly (p < 0.01) among osteotomy patterns and between each osteotomy characteristic. Regardless of the osteotomy pattern, higher numbers of osteotomies significantly (p < 0.05) correlated with reductions in reaction force and maximum stress. An X-shaped configuration with three osteotomies deep and wide to the bone was biomechanically the most favorable model. ConclusionInner cortical bone layer osteotomy might be an effective modification to the conventional FOA approach in terms of predictable shaping of the orbital bandeau.

Crashworthiness Analysis of Self-Similar Nested Hierarchical Hexagonal Tubes

To enhance the crashworthiness of thin-walled structures, this study proposes a self-similar nested hierarchical hexagonal tube. This innovative design incorporates the hierarchical technique into the structural configuration of hexagonal thin-walled tubes. Numerical analysis, conducted using a validated finite element model, reveals that the proposed self-similar nested hierarchical hexagonal tube (SNHHT) significantly enhances energy absorption compared to traditional hexagonal tubes, maintaining consistent wall thickness and mass conditions. Particularly noteworthy is the improvement in energy absorption indexes under the same mass condition, with SNHHT-4 demonstrating enhancements of up to 76.45% and 86.84% in energy absorption and crushing force efficiency, respectively, while concurrently achieving a 4.11% reduction in initial peak crash force. Subsequently, a parametric study exploring wall thickness, shape factor, and various rib thicknesses was performed to investigate structural crashworthiness. Finally, employing the simplified super-folded element method, the theoretical formulation of mean crushing force was derived, and its accuracy was validated through numerical simulations.

Seismic design-assisted-by-testing approach for racks with dissipative baseplates in the cross-aisle direction

A design-assisted-by-testing strategy is proposed for the upright frames of adjustable pallet racks. This methodology defines a procedure that aims to locate marked post-elastic behavior at the floor-to-upright connections of lateral resisting frames in the cross-aisle direction. Such connections are intended to enhance the performance of the cross-aisle frames when subjected to dynamic forces in their plane. The chosen baseplate connection is experimentally tested using monotonic and cyclic protocols at the Steel Structures Laboratory of the National Technical University of Athens (Greece). Then, a numerical model of the baseplate is calibrated using literature parameter definitions and hence validated using physical data. Additionally, the dynamic response of two upright frames is numerically investigated: one with traditional hinge connections and another with dissipative ones. This study indicates that the proposed procedure successfully enhances ductility, resulting in a significant reduction (up to 50%) in upright axial forces compared to the conventional configuration. Finally, the open-source code for ground motion selection, together with its database, is released.

Improving the energy efficiency and carbon dioxide reduction of a long-haul bus through aerodynamic design optimization

&lt;p&gt;Exhaustion of fossil fuel resources, inconsistent fuel costs and the difficulty of adopting electric vehicle technology in commercial vehicles support the idea that there is an opportunity for research in public transit regarding the correlation between energy efficiency and aerodynamic drag. The turbulent external airflow over a bus at high speeds impacts acceleration, speed, and fuel economy. The fundamental bus's design is intended to carry enough passengers for a reasonable run. Envisaging the factors influencing aerodynamic drag is defiant due to the convoluted relationship between the moving bus and the air. Consequently, a comprehensive numerical and experimental exploration is executed on the bodywork of a bus to improve its aerodynamic efficiency. The aerodynamic drag is directly proportional to the variations in the air density, frontal area, freestream velocity and the drag coefficient. Minimal design reforms are performed on a distinctive long-haul bus. The exertion aims to minimize the drag coefficient, thereby improving the flow characteristics of the bus's bodywork. Through the shape optimization of the bus's bodywork, the modified design has attained a forty-five percent reduction in the drag coefficient. This substantial reduction in drag coefficient directly impacts the reduction of drag force, energy efficiency improvement, and carbon emissions reduction.&lt;/p&gt;

Investigating Twist Drill Design Influence on Thrust Force and Surface Roughness in Drilling AFRP/ Al7075-T6 Stacks Materials

Drilling Aramid Fiber-Reinforced Plastic (AFRP) presents unique challenges when compared to drilling other composite panels. These difficulties arise from the high-toughness characteristics of aramid fibers, which exhibit a tendency for ductile deformation during the drilling process. This research explores the influence of drill bit design on the drilling process stack-up materials, which comprise Aramid Fiber Reinforced Plastic Composite Laminates (AFRP) and Aluminum Al7075-T6. Three distinct bit designs were employed in the experiment, conducted on a Computer Numerical Control (CNC) machine operating at a spindle speed of 2000 rev/min and a feed rate of 0.05 mm/rev. To measure thrust force during drilling, a dynamometer was integrated into the setup. Subsequently, a roughness tester was utilized to assess the hole surface roughness of the stack-up materials. For AFRP materials, the w-point drill design emerged as the optimal choice, reducing thrust force by approximately 5% to 13% compared to other drill bit designs. Conversely, for Al7075-T6 panels, the tapered web drill design demonstrated exceptional results, lowering thrust force by approximately 21% and 50% in comparison to burnishing and w-point drill bits, respectively. In terms of hole surface roughness, the burnishing drill type consistently produced the smoothest surfaces, boasting significant improvements of 44% and 82% when compared to the tapered web and w-point drill bits for AFRP panels. Similarly, for Al7075-T6 panels, the burnishing drill type consistently outperformed the tapered web and w-point drill bits by 74% and 88%, respectively, in achieving a superior hole surface finish. These findings underscore the critical importance of selecting the appropriate drill bit design to optimize thrust force reduction and hole surface quality when working with stack-up materials.

Atomistic perspective of anti-friction performance in graphene-coated multi-principle-element alloys

Multi-principal-component alloys (MPCAs) have received considerable attention due to their excellent strength, ductility, and the relatively low wear resistance, which limits their practical applications. One strategy for mitigating the detrimental effects of friction is to coat the alloy surfaces with graphene. Nevertheless, the deformation mechanism under wear at the atomic scale remains unclear. In this study, the wear behavior and hardening mechanism of the graphene-coated FeCrNi multi-principal-component alloy were investigated through molecular dynamics simulations. The results demonstrated that the graphene layer significantly improves the wear resistance of the FeCrNi MPCA substrate, with a reduction in the friction force and friction coefficient of 23.92 % and 68.36 %, respectively. In particular, the graphene coating acts as a powerful barrier, limiting the propagation of dislocations and promoting the generation of massive immobile dislocations, resulting in a significant hardening effect. Concurrently, the graphene coating effectively mitigates contact stress and surface thermal softening, which suppresses the accumulation of atoms and enhances the wear resistance. These findings provide theoretical insights into the friction behavior of graphene-coated MPCAs, paving the way for the achievement of superior surface properties in MPCAs.

Striking Differences in Kendo Headgear.

Kendo, a martial art developed by the samurai, is rooted deep in Japanese culture with traditional armor that has seen little change over the past centuries.Despite its century-old design, kendo helmets are manufactured without third-party testing to verify their quality and effectiveness against head trauma. To evaluate the effectiveness of different helmet stitching patterns and padding materials in mitigating impact forces that could lead to sports-related concussions (SRC) in kendo, and to assess variations in safety performance across different genders and kendo ranks (Dan and Kyu). We collected data from 10 kendo practitioners (six males and four females), analyzing over 4,000 strikes using shinai on a sensor-equipped mannequin. Various helmet stitching patterns (ranging from 2 mm to 9 mm) and padding types (polyurethane-based and different thicknesses of cotton-based pads) were tested under controlled conditions simulating realistic impacts encountered in kendo practice. The results indicated that helmets with wider stitching patterns (e.g. 8 mm and 9 mm) generally offered better energy absorption, exhibiting statistically significant lower mean g-forces with a 95% confidence interval compared to tighter patterns (2 mm, 4 mm, 6 mm, and 8 mm x 2 mm) (p < 0.001). Additionally, the polyurethane-based padding outperformed cotton-based padding by a statistically significant reduction of impact force (p < 0.001). Significant differences in striking force were also observed between genders and ranks, with male and higher-rank (Dan) practitioners delivering stronger impacts (both p < 0.001). This study highlights the critical influence of helmet stitching patterns and padding materials on the protective capabilities against concussions in kendo. Even though helmets with narrower stitching patterns cost more, helmets with wider stitching patterns and polyurethane padding material provide enhanced safety benefits. We do not know how the difference in striking force between genders and ranks affects the outcome of a kendo match.

Optimizing shear-thickening fluid microencapsulation with high-temperature pickering emulsion for enhanced impact-resistant materials

Combining shear-thickening fluid (STF) with matrix material enables the creation of high-performance materials with enhanced impact resistance. However, effectively preventing STF leakage and avoiding potential reactions between the fluid and the matrix material remain notable challenges. Encapsulating STF through emulsion templating offers a viable solution to these issues. Traditional emulsion templating methods require adding extra solvents to STF to counteract the hindrance of shear-thickening on emulsification, accompanied with increased costs and environmental pollution, and difficulties in maintaining the integrity of core components. In this study, we developed STF microcapsules using a novel high-temperature Pickering double emulsion technique. Our investigation into the rheological properties of molecular sieve/diols suspensions demonstrates that the shear thickening effect could be controlled by particle concentration, surface charge of particles and solvent viscosity. Octadecyltrimethoxysilane-modified fumed silica and fumed silica were utilized as stabilizers for STF-in-paraffin primary emulsions and STF-in-paraffin-in-propylene glycol secondary emulsions, respectively. As temperature increased, droplet sizes of the primary emulsion were significantly reduced. The Pickering emulsion approach effectively preserves the STF composition by forming robust barriers at the emulsion interface with silica particles. Typical STF microcapsules were incorporated into a silicone rubber matrix, the composites exhibited a significant decrease in resilience and an enhanced impact resistance with a 20.9% reduction in maximum impact force. This study is the first to suggest the application of the high-temperature Pickering double emulsion technique for the microencapsulation of STF, offering a practical and scalable method without diluting the STF, thereby ensuring the controllability of the core components.

Hard/stiff surface coatings for particle weakening, part I: Methodology

Size-reduction processes are essential for liberating valuable minerals yet energy-inefficient, which needs to be remedied by developing energy-efficient methods. This work is the first part of a wide study that (i) describes a surface coating method, namely, spray coating, and (ii) presents some preliminary results that hard or stiff surface coatings can be used to weaken softer ore particles. The hard surface coatings were achieved with a ceramic spray and two inorganic precipitates (CaCO3 and silica). The fracture energy and/or strength of spray-coated and uncoated particles was measured using the Short Impact Load Cell (SILC). Spray coating can only yield low surface coverage (up to 1–2% of the mass of particles), which is only apparent if particle surfaces are washed before coating. Nevertheless, the preliminary results suggest significant reductions in the fracture force and energy of soft ore particles after they are coated.

Monotonic testing of brace assemblies for piping systems and considerations for capacity design

Distributed nonstructural elements (NSEs), such as piping systems, are restrained against seismic actions using proprietary or, at times, custom-designed braces. The strengths of these elements are provided in the component brochures published by the manufacturers, with no information on their deformation capacities. Previous research on the seismic performance of NSEs provide several formulations to calculate possible reductions in design force by relying on ductility capacity of their seismic restraints. However, designers require a realistic estimate of the ductility capacity of the seismic restraints to use these formulations. This paper discusses the results of a test program on the behavior of brace assemblies under monotonic tensile and compression loading. The results are used to identify the potential failure modes of the tested brace assemblies and to quantify their ductility capacity. Further, design examples are presented to highlight the need for the use of capacity design principles in the design of brace assemblies and their anchors.

Exploring memory mechanisms for friction fatigue in vibratory pile driving

This paper studies the mechanism that leads to the reduction of frictional soil reaction forces during pile driving, termed friction fatigue. We focus on axial vibratory driving, an environmentally friendly monopile installation method, and examine two friction fatigue formulations, i.e. a penetration-based and a cyclic memory mechanism. Friction fatigue plays a pivotal role in pile drivability and post-installation bearing capacity for piles installed via axial vibratory driving. Through numerical analyses and validation against field data from onshore experiments, the efficacy of these memory mechanisms is assessed. The results reveal that the proposed cyclic memory mechanism provides consistently more accurate predictions than the corresponding penetration-based approach, offering a promising option for modelling friction fatigue in vibratory driving. This study advances our understanding of friction fatigue in the context of vibratory driving for offshore monopile installation, emphasizing the need for further numerical and experimental works in this topic.

Optimizing drilling parameters for fly ash-filled hemp/epoxy composites: investigating drill bit geometries, feed rates, and spindle speeds

This article investigates the drilling behavior of hemp fiber-reinforced epoxy composites, both unfilled and fly ash-filled. Drilling performance tests were conducted at varying feed rates (8, 16, and 24 mm min−1) and spindle speeds (700, 1400, and 2100 RPM) using three drill geometries: parabolic, 8-facet, and dagger. The fly ash-filled hemp/epoxy composite showed significant reductions in maximum thrust force (25.09%, 19.92%, and 21.43%) and torque (80%, 79.87%, and 59.25%) when drilled with parabolic, 8-facet, and dagger drill bits, respectively, compared to the unfilled composite. The maximum drilling temperature reached 90.6 °C during cutting and decreased to 71.7 °C post-drilling. Overall, the fly ash-filled composites demonstrated superior performance in terms of drilling-induced stresses and damage.

Impacts and depositional behaviors of debris flows on natural boulder-negative Poisson's ratio anchor cable baffles

The impacts of natural boulders carried by debris flows pose serious risks to the safety and reliability of structures and buildings. Natural boulders can be highly random and unpredictable. Consequently, boulder control during debris flows is crucial but difficult. Herein, an eco-friendly control system featuring anchoring natural boulders (NBs) with (negative Poisson's ratio) NPR anchor cables is proposed to form an NB-NPR baffle. A series of flume experiments are conducted to verify the effect of NB-NPR baffles on controlling debris flow impact. The deployment of NB-NPR baffles substantially influences the kinematic behavior of a debris flow, primarily in the form of changes in the depositional properties and impact intensities. The results show that the NB-NPR baffle matrix successfully controls boulder mobility and exhibits positive feedback on solid particle deposition. The NB-NPR baffle group exhibits a reduction in peak impact force ranging from 29% to 79% compared to that of the control group in the basic experiment. The NPR anchor cables play a significant role in the NB-NPR baffle by demonstrating particular characteristics, including consistent resistance, large deformation, and substantial energy absorption. The NB-NPR baffle innovatively utilizes the natural boulders in a debris flow gully by converting destructive boulders into constructive boulders. Overall, this research serves as a basis for future field experiments and applications.

A novel vortex control method for improving anti-overturning performance of a high-speed train with leeward airbag structures under crosswinds

The high-speed train's head and cross sections have been designed in an innovative way to meet the requirements of aerodynamic drag reduction and crosswind stability of the train. However, with the continuous increase in the running speed of high-speed trains and the continuous reduction of the total weight of the car body, it is critical to develop new strategies to ensure train safety in crosswind environment. In the current study, a novel vortex control method with airbag structure installation on the leeward side (LWS) of the train was proposed to disturb the leeward large vortices, with expectation to weaken the vortices adjacent the train body and increase the surface pressure on the leeward side. The leeward airbag structures (LASs) contribute to reducing the pressure difference between the windward and leeward sides of the train body. As a result, a reduction of the lateral force and overturning moment coefficients is obtained. An amazing observation is that an extra lift force is achieved by LASs, which leads to an anti-overturning moment, further improving the anti-overturning performance of the high-speed train. Compared with the original model, the LASs can decrease the lateral force coefficients by 7.1%, while the lift coefficient is increased by 12.8%, which together reduces the overturning moment coefficient by 13.1%. It indicates that the main influence factor for crosswind stability of the train tends to be changed after the installation of LASs. The aerodynamic performance of the tail car is more sensitive to the LASs as compared to that of the head and middle cars, i.e., the reduction of the overturning moment coefficient is about 44.6% for the tail car, whereas it is only 7.8% and 12.5% for the head and middle cars, respectively. Thus, the LASs proposed in the current work can significantly improve the anti-overturning performance of high-speed trains, which will provide a novel anti-overturning approach for higher-speed trains.

A foundation model enhanced approach for generative design in combinational creativity

In creativity theory, combining two unrelated concepts into a novel idea is a common means of enhancing creativity. Designers can integrate the Additive concept into the Base concept to inspire and facilitate creative tasks. However, conceiving high-quality combinational ideas poses a challenge that combinational creativity itself demands the consideration of conceptual reasoning and synthesis. We propose an AI foundation model enhanced approach for supporting combinational creativity. This approach derives combinational embodiments, and assists humans in verbalising and externalising combinational ideas. Our experimental study demonstrates that the generated combinational ideas by the approach obtained highest scores compared to those ideas generated without an AI foundation model or combinational strategy. We built a combinational creativity tool called CombinatorX based on this approach to generate ideas. In a study with the comparison of an existing combinational creativity tool and Internet search, we validated that our approach improves the effectiveness of combinational idea generation, enables a reduction in labour force, and facilitates the refinement of combinational ideation.