Bending Stress Research Articles

Roof movement and instability fracture characteristics in shallow-buried thin coal seam conventional mining faces

The variation in the width of the mining face significantly affects the stability of the face, leading to potential roof fracturing and collapse. Additionally, strong mining pressure can manifest, severely impeding the safe production of coal mines. This study uses the No. 16705 conventional working face of Jinda Coal Mine as its engineering background to investigate the characteristics of roof strata movement and instability under conditions of variable-width mining in shallow-buried thin coal seams. First, the dynamic load of the roof strata is estimated based on the key strata theory. Next, a mechanical model of the immediate roof strata movement in the working face is established based on the theory of elastic thin plates, which has been used to reveal the impact of different dimensions of the overhanging plate structure and residual overhanging structures in the corner on roof movement and its associated fracture mechanics. The findings indicated that the maximum bending deformation, deformation moment, and bending stress all have an exponential function relationship with the roof width. Similarly, these metrics have an exponential function relationship with the overhanging span of the roof. In addition, these parameters all have a linear functional relationship with the size of the residual overhanging structures in the corner. Finally, the effect of roof instability on overlying pressure is analyzed, and both the initial fracture step length and cyclic movement fracture step length of the roof are estimated. These insights offer valuable scientific guidance and a theoretical foundation for analyzing the adaptability of load-bearing pillars pressure in thin coal seam mining faces, bearing significant relevance to safety production.

Genome-wide association studies for a comprehensive understanding of the genetic architecture of culm strength and yield traits in rice.

Lodging resistance in rice is a complex trait determined by culm morphological and culm physical strength traits, and these traits are a major determinant of yield. We made a detailed analysis of various component traits with the aim of deriving optimized parameters for measuring culm strength. Genotyping by sequencing (GBS)-based genome-wide association study (GWAS) was employed among 181 genotypes for dissecting the genetic control of culm strength traits. The VanRaden kinship algorithm using 6,822 filtered single-nucleotide polymorphisms (SNPs) revealed the presence of two sub-groups within the association panel with kinship values concentrated at<0.5 level, indicating greater diversity among the genotypes. A wide range of phenotypic variation and high heritability for culm strength and yield traits were observed over two seasons, as reflected in best linear unbiased prediction (BLUP) estimates. The multi-locus model for GWAS resulted in the identification of 15 highly significant associations (p< 0.0001) for culm strength traits. Two novel major effect marker-trait associations (MTAs) for section modulus and bending stress were identified on chromosomes 2 and 12 with a phenotypic variance of 21.87% and 10.14%, respectively. Other MTAs were also noted in the vicinity of previously reported putative candidate genes for lodging resistance, providing an opportunity for further research on the biochemical basis of culm strength. The quantitative trait locus (QTL) hotspot identified on chromosome 12 with the synergistic association for culm strength trait (section modulus, bending stress, and internode breaking weight) and grain number can be considered a novel genomic region that can serve a dual purpose of enhancing culm strength and grain yield. Elite donors in the indica background with beneficial alleles of the identified major QTLs could be a valuable resource with greater significance in practical plant breeding programs focusing on improving lodging resistance in rice.

Investigating the influence of peak internal air temperature (PIAT) on material characteristics of linear low-density polyethylene (LLDPE) during rotational moulding

In present study, six samples of ICORENE 1613 LLDPE fuel tank with homogeneous composition were analysed for six different PIAT values of 165 °C, 170 °C, 180 °C, 190 °C, 195 °C and 200 °C in the first stage. In the second phase of the study, the samples with optimum PIAT values were considered for the Tensile and Flexural strength study at different temperatures. Peak Internal Air Temperature (PIAT) values were obtained using the rotolog instrument, while the tensile and flexural tests were performed utilizing the Universal Testing Machine for accurate characterization of the material properties. The tensile and flexural strength were carried out at three different operating temperatures considering the tank will be subjected to variable operating conditions in real world exercise. The maximum value for both all the process parameters studied were observed at PIAT value of 195 °C, the same has been chosen for the further investigation. The failure data obtained from these two destructive testing will be helpful to mitigate the defects during the process. The tensile test results indicate that the LLDPE sample exhibits the maximum tensile strength of 17.3 MPa at 23 °C and the highest elongation percentage at failure, which is 182.7% at 80 °C. Moreover, the sample shows a remarkable flexural strength of 75.97 MPa at 23 °C, which is indicative of its superior ability to resist deformation under applied bending stresses.

Effect of tooth root fillet on root bending stress

The tooth root fillet exerts a significant effect on the root bending stress of gear teeth. However, the current study predominantly focuses on theoretical analysis and numerical methods, with insufficient emphasis on effective experimental verification. Therefore, this paper completes root bending stress tests on gear teeth and conducts an analysis of how the tooth root fillet impacts root bending stress. Firstly, the paper provides a summary of the generation theory of the tooth root fillet using rack cutters/hobs, which serves as the foundational machining principle for tooth root fillet. Secondly, using three typical tooth root fillet as examples, the study conducts root bending stress tests. The R-S-N curves corresponding to these three tooth root fillet profiles are derived using both conventional group methods and a variable load approach, involving lifting and lowering. Finally, the paper analyses the influence of these three types of tooth root fillet on the root bending stress of gear teeth. Through a comparison of S-N curves at the same reliability level, it identifies the optimal tooth root fillet among the three.

Warping Torsion in Sandwich Panels: Analyzing the Structural Behavior through Experimental and Numerical Studies.

Recently, there has been a growing interest in the use of sandwich panels that, beyond handling well-known bending stress, can withstand torsional stresses. This is particularly relevant for wall applications when the panels are equipped with photovoltaic or supplemental curtain wall modules. This research article presents a detailed exploration of the structural behavior of eccentrically loaded sandwich panels, with a specific focus on warping torsion. Experimental and numerical studies were conducted on polyisocyanurate (PU) core sandwich panels, commonly employed in building envelopes. These studies involved various dimensions and material properties, while omitting longitudinal joints. The experimental study provided essential insights and validated the numerical model in ANSYS. Enabling parametric variation, the numerical analysis extends the analysis beyond the experimental scope. Results revealed a high degree of correlation between experimental, numerical, and analytical solutions, regarding the rotation, as well as the normal and shear stress of the panel. Confirming the general applicability of warping torsion in sandwich panels with certain limitations, the study contributes valuable data for applications and design of eccentrically loaded sandwich panels, laying the foundation for potential engineering calculation methods.

Influence Law of Axis Deflection on the Mechanical Properties of Steel Stranded Short Slings in Arch Bridges

Most cable arch bridge damage accidents are caused by bridge collapse due to fracture of the short sling of the arch bridge. The service life of the short sling is much lower than the design life, mainly resulting from the action of vehicles and temperature, and the arch rib and the bridge floor will have relative displacement along the bridge direction, which leads to the emergence of bending stress due to the different axes at both ends of the short sling, forming local stress concentration. The stress concentration is coupled with corrosion to accelerate the damage to the sling. To study the influence of shaft deflection on the mechanical properties of short slings of steel strands in arch bridges, this study analyzes the distribution law of the shaft deflection angle of arch bridge slings under the action of vehicle and temperature loads for a medium-bearing arch bridge with a main span of 560 m. The results show that under different vehicle and temperature loads, the axial deflection angle of the short sling is the largest, and the closer it is to the center of the span, the smaller the axial deflection angle. The static and fatigue properties of 1, 3, 7, 9, 12, 19, and 27 strands of whole bunch extruded strand slings were simulated and analyzed under a 0.45σb force when the axial deflection angle of the strand slings was 0 mrad, 10 mrad, 20 mrad, and 30 mrad. The results show that the ultimate tensile properties, breaking strength, and fatigue life of the strand slings decreased to a certain extent with increasing shaft deflection angle. The accuracy of the finite element models is verified by the ultimate tensile test and the fatigue test. This study explores the bending deflection results of the short slings of arch bridges due to the different axes of the upper and lower anchorages and provides the necessary theoretical support for the design and fatigue life estimation of the short slings of arch bridges.

Indolocarbazole‐Based Small Molecule Cathode‐Active Material Exhibiting Double Redox for High‐Voltage Li‐Organic Batteries

Most organic electrode materials (OEMs) for rechargeable batteries employ n‐type redox centers, whose redox potentials are intrinsically limited &lt;3.0 V versus Li+/Li. However, p‐type materials possessing high redox potentials experience low specific capacities because they are capable of only a single redox reaction within the stable electrochemical window of typical electrolytes. Herein, we report 5,11‐diethyl‐5,11‐dihydroindolo[3,2‐b]carbazole (DEICZ) as a novel p‐type OEM, exhibiting stable plateaus at high discharge potentials of 3.44 and 4.09 V versus Li+/Li. Notably, the second redox potential of DEICZ is within the stable electrochemical window. The mechanism of the double redox reaction is investigated using both theoretical calculations and experimental measurements, including density functional theory calculations, ex situ electron spin resonance, and X‐ray photoelectron spectroscopy. Finally, hybridization with single‐walled carbon nanotubes (SWCNT) improves the cycle stability and rate performance of DEICZ owing to the π–π interactions between the SWCNT and co‐planar molecular structure of DEICZ, preventing the dissolution of active materials into the electrolyte. The DEICZ/SWCNT composite electrode maintains 70.4% of its initial specific capacity at 1‐C rate and also exhibits high‐rate capability, even performing well at 100‐C rate. Furthermore, we demonstrate its potential for flexible batteries after applying 1000 bending stresses to the composite electrode.

Flexible Artificial Mechanoreceptor Based on Microwave Annealed Morphotropic Phase Boundary of HfxZr1‐xO2 Thin Film

AbstractThe development of artificial tactile receptor systems is important in the fields of prosthetic devices, interfaces for the metaverse, and sensors. A pressure sensor and memory device may be used in this system to replicate the tactile detecting capabilities of human skin. The implementation of systems that take into account mass production and miniaturization is still difficult. Here, a flexible artificial tactile receptor built using conventional semiconductor processes that combine a vertically stacked piezoelectric sensor with neuromorphic memory is presented. As a fundamental component for both sensors and memory, hafnium zirconium oxide (HZO) formed by using semiconductor deposition technique is introduced. Due to its exceptional piezoelectric performance, the morphotropic phase boundary of HZO is studied. The entire materials and processes are highly compatible with conventional semiconductor processes, including microwave annealing‐based low‐temperature crystallization. Even after 10,000 times of bending stress, the sensor and memory constructed on a flexible substrate exhibit consistent pressure detection characteristics over a wide range of 2–25 kPa. The feasibility of the approach is further demonstrated by a deep neural network simulation, which reached 90.8% braille recognition accuracy. Wearable electronics and medical devices are two examples of industrial domains that can use these flexible, exceptionally durable devices.

Damage mechanisms of spline teeth of friction plates under non-uniform impact

The fatigue fracture failure of friction plates seriously affects the safety of high-power density transmission systems due to the non-uniform impact with the inner hub. However, the crack initiation inducement and underlying damage mechanisms are still confused so far, which has critical significance for improving the service life. To address this problem, the matrix metallographic structure of friction plates was observed by Scanning Electron Microscope (SEM), which excludes internal defects within the organization. Then, an impact dynamic model was established to investigate the collision laws between spline teeth and the inner hub. The effect of the inner hub’s speed fluctuations on the impact force and acceleration was analyzed, and an analytical relationship between tooth root stress, impact force, and gear parameters was established. A large module simulation prototype test rig was designed based on the proposed equivalent model to verify the impact dynamic model. Results show that the majority of collisions between spline teeth and the inner hub are “catch-up collisions”, which well explains the non-uniform impact phenomenon. The “frontal collisions” will only occur when the speed of the inner hub is lower than that of the friction plate. The higher cumulative frequency of tensile stress on the pull side of spline teeth roots by “catch-up collisions” reveals the underlying mechanism for the differential extent of cracks’ damage. The minimum bending stress of the teeth root is 125.5 MPa at a pressure angle of 32°, which shows a linear increase with tooth clearance. The fatigue fracture of friction plates has been effectively suppressed after structural optimization.

Investigation of longitudinal movements of girder ends considering various longitudinal non-linear resistances in railway suspension bridges

The functionality of expansion joints, bearings, and dampers in suspension bridges is directly impacted by the longitudinal movement of the girder ends. The complex longitudinal resistance of the girder significantly influences this movement in railway suspension bridges. This study develops an analytical model of a railway suspension bridge using measured displacement. The model encompasses various longitudinal nonlinear resistances, including girder-rail interaction, bearing friction, and viscous dampers, enabling a detailed analysis of longitudinal motion characteristics and deformation patterns of girder ends under train loads. This study investigates the effects of various longitudinal resistances on the movement of the girder and stress within the connecting components. A novel central buckle design is proposed to reduce the stress amplitude of the central buckles in railway suspension bridges. Results show that the innovative analysis model can accurately assess the longitudinal movement of girder ends in railway suspension bridges, aligning closely with the measured. The girder displays minimal longitudinal movement under train loads, owing to the longitudinal nonlinear resistances. However, there is a significant relative longitudinal displacement between the cable and girder in short hangers, leading to a considerable increase in bending stress and vast stress in the central buckle. Consequently, when studying the longitudinal movement in railway suspension bridges, it is critical to comprehensively analyze the longitudinal displacement of girder ends and the stress across various bridge components. The novel central buckle effectively mitigates excessive stress on the central buckle during train passage and simultaneously alleviates bending stresses of the short hangers. The findings of this study offer invaluable theoretical direction and practical engineering insights for the rational design of railway suspension bridges.

Comparison of stiffness degradation in fatigue-loaded concrete cylinders and large-scale beams

Wind and wave loads subject the tower structures of wind turbines to bending stress. The resulting initial linear strain gradients in the tower cross-section cause fatigue-induced degradation of the concrete at the outer edge of the structures. As the number of load cycles increases, stresses are gradually redistributed to the inner cross-section of the structure consequently. Most of the test results documented in the literature were obtained from small-scale concrete specimens or small-scale components. In those cases, the stiffness and stress redistributions occurring in the real component can only be insufficiently derived, and possible scale effects cannot be taken into account. Besides, available test results for individual component tests are mostly only for load cycles up to 2⋅106. However, significantly lower load levels and thus higher number of load cycles are expected to occur in wind turbines compared to usual fatigue tests. To deal with this issue, extensive fatigue tests on small cylindrical specimens as well as large-scale beams in the very-high-cycle fatigue range are carried out in this work. The test results of both cylindrical and beam specimens show the typical three-phase stiffness curves known from the literature. These curves exhibit a disproportionate decrease at the beginning of the loading, followed by a constant decrease in stiffness, and finally, a greater decrease in stiffness shortly before failure. Moreover, the stiffness curves from the tests on both specimen types show good agreement. It can be concluded that the results from small cylindrical specimen tests can be transferred to large-scale structural components.

Design and transmission performance analysis of planthopper hip joint gear

To enhance the efficiency and load-carrying capacity of the jumping robot’s transmission system, the transmission characteristics of the planthopper hip gear were analyzed. The analysis revealed that the gear pair exhibited low transmission errors, high transmission efficiency, and significant torque capacity, making it suitable for high-speed, high-precision, and high-power density transmissions. A bionic design study of the jumping robot’s gear was conducted, drawing inspiration from the planthopper hip gear’s tooth shape and profile. A logarithmic spiral was assumed as the tooth profile based on its consistent pitch angle and curvature gradient characteristics. Parameters of the tooth profile of the bionic gear were calculated, and equations for the tooth surface were derived. A three-dimensional model of the bionic gear was constructed, and both its transmission efficiency and error were calculated. Using the finite element method, theoretical formulas for contact stress and bending stress in the bionic gear were deduced. The distribution characteristics of both bending and contact stress were analyzed, demonstrating that the bionic gear used in high-performance jumping robots possesses low transmission error, high transmission efficiency, and excellent contact strength, providing a theoretical foundation for enhancing their jumping capabilities.

Mechanical Response Analysis of Regular and Lightweight Concrete under Bending Stresses

This study investigated the mechanical response of regular and lightweight concrete under bending stresses. We compared the stress‐strain relationships, densities, and deformation capacities of these two types of concrete to highlight their key differences. Lightweight concrete, with a lower density of 1800 kg/m³, offers significant weight reductions, making it ideal for applications with weight constraints. However, this reduced weight results in lower compressive and flexural strengths. On the other hand, normal concrete, with a density of 2400 kg/m³, exhibited higher mechanical strength and durability. The stress‐strain graphs from the study showed that both concrete types exhibit both elastic and plastic deformation, with a transition from elastic to plastic behavior at specific stress points. By balancing weight reduction against mechanical strength, this study provides valuable insights for construction professionals in selecting the appropriate concrete type for various projects.

Reduction in bending stress in magnetostrictive vibration sensor devices using concave-convex spherical contact

Reduction in bending stress in magnetostrictive vibration sensor devices using concave-convex spherical contact

Reduction in bending stress in magnetostrictive vibration sensor devices using concave-convex spherical contact

Reduction in bending stress in magnetostrictive vibration sensor devices using concave-convex spherical contact

Experimental investigations: Reinforced Concrete Beams Bending Strength with Brine Wastewater in Short Age

The scarcity of waste in some regions has led to the contemplation of other approaches to providing potable water for human use. In the present research, it is proposed that a portion of the brine wastewater be recycled for potable water purposes through its incorporation into concrete and reinforced concrete compositions. The researchers performed an extensive empirical investigation to examine the impact of incorporating brine wastewater into the concrete mixture on the shear strength, bending stress, and compressive strength of the material. A total of seventy-two beams, each measuring 500 mm in length, 100 mm in width, and 100 mm in depth, were observed. A total of twelve beams were designated as control specimens, while an additional sixty beams were subjected to immersion in brine wastewater at varying concentrations of 2.5, 5, 7.5, 10, and 15%. The beams were reinforced using two longitudinal steel bars with a diameter of 8 millimeters in the tension zone and 6 millimeters in the compression zone. The stirrups included in the study were also measured to have a diameter of 4 mm. The samples were examined at intervals of seven, fourteen, twenty-one, and twenty-eight days. Based on the findings of this study and other relevant studies, it was determined that the use of 10% fresh water as a substitute for brine wastewater yielded the most optimal outcomes. The results obtained after a duration of 28 days indicate a notable increase in both the compressive and bending strengths of the concrete samples, with improvements of around 22% and 2.6% seen in comparison to the reference specimens. The impact of brine wastewater on the corrosion of reinforcing steel in reinforced concrete was investigated. The empirical findings indicated that the introduction of brine wastewater at a concentration of 10% to the concrete constituents did not provide any discernible repercussions over a period of 65 days. Doi: 10.28991/CEJ-2024-010-01-010 Full Text: PDF

Mechanical Properties and Stress Analysis of Natural Fiber Reinforced Polymer Composite Spur Gear

This research study investigates the mechanical properties of polymer composites reinforced with natural fibers, specifically Palmyra palm leaf stalk fiber (PPLSF) and Palmyra palm primary leaf stalk fiber (PPFLSF). Tensile, flexural, and impact strength were among the composites’ mechanical parameters generated by integrating these fibers into a polymer matrix and assessing them experimentally. Additionally, stress analysis of a spur gear was conducted using the finite element analysis software ABAQUS. The composite material properties obtained from the experimental investigation were used in the analysis to evaluate the gear’s stress distribution and deformation behavior. The bending stress at the pitch point of the natural composite gears for PPLSF, PPFLSF, and nylon synthetic material is analyzed using analytical and experimental methods by ABAQUS software. Finally, the results are compared with each other. The results show that stress induced by nylon is comparatively higher than that of PPLSF and PPFLSF fiber. By analyzing these composites’ strength, durability, and stress distribution under operating environments, the study aims to determine whether they are suitable substitutes for conventional materials.

Electrothermal Distortion Analysis and Structural Strain Assessment of Vehicle Cable Terminals Under Bending Stresses

Electrothermal Distortion Analysis and Structural Strain Assessment of Vehicle Cable Terminals Under Bending Stresses

Effect of the charge rate on the mechanical response of composite graphite electrodes: in situ experiment and mathematical analysis.

The cycling lifespan and coulombic efficiency of lithium-ion batteries are crucial to high C-rate applications. The Li-ion concentration is crucial in determining the mechanical integrity and structural stability of electrodes. In this work, graphite is selected as the working electrode due to its widespread use in the electric vehicle industry. The experimental data have shown that the electrodes with a mass loading of 6.54 mg cm-2 exhibited poor cycling performance and high charge transfer resistance at high charge rates. To explain this phenomenon, an in situ stress measurement system and a C-rate-dependent stress model are established to study the mechanical properties of the composite graphite electrode during the electrochemical process at various C-rates. Moreover, the effect of the Li-ion concentration-dependent modulus and C-rate-dependent partial molar volume is taken into account in the mathematical model. The computational curvature data fit well with the corresponding experimental data, highlighting the importance of considering lithium-ion concentration in mechanical stress. It has been found that stresses along the thickness of the active layer switch between compressive and tensile stresses due to the competition between bending stress and diffusion-induced stress. The stress at the outer surface of the composite graphite electrodes reaches a maximum magnitude of 27.5 MPa at a 1.5C-rate. In contrast, the stress at the interface of the active layer is maximum at a 0.5C-rate due to the existence of more lithium ions. Our study provides a direct insight into the quantitative analysis of electrode stresses at different C-rates.

Fatigue strength of synthetic rope: experimental methodology

Crane industries and industrial lifting companies aims to reduce the overall weight of the winch and limit the systematic use of steel wire rope in order to increase their competitiveness. This overall weight reduction can result from the lightering of the rope using synthetic material. Metallic rope fatigue behaviors are well documented and criteria for maintenance are established in the ISO 4309 standard unlike non-metallic ropes fatigue behaviors. Many unknowns remain, as failure modes, fatigue strength, ratting criteria, tribological behavior and friction, etc...In this context, CETIM and its industrial partners have launched, within a working group, a research program to evaluate the fatigue performance of synthetic ropes subjected to periodic bending stress. A specific scale 1:1 test bench which simulates the winding of the rope around the pulleys and drums was developed and Fatigue tests was performed on synthetic ropes. This test bench can be used on several rope geometries and dimensions, material (aramid, HMPE…), and loadings.This paper presents the test bench and discusses the experimental methodology developed to test synthetic ropes in fatigue bending mode.