Bending Stress Research Articles

Fatigue Life Estimation under High Temperature and Variable Loading of AA7001-T6 Using Shot Peening

In this study, the fatigue life of aluminum alloys (7001-T6) was predicted with shot peening at various temperatures. Surface treatment with shot peening steel balls is a mechanism for reducing damage. An experimental investigation was conducted to find the degree of fatigue accumulation for AA7001-T6 under rotational bending loading and stress ratio R = −1. The experiments were conducted at RT (25 ℃), 330 ℃, and SP + 330 ℃ temperatures. A modified damage stress model that considers damage at various load levels was recommended for forecasting the fatigue life under high temperatures. The model and experimental results were compared to determine the most damage (Miner’s rule). The experimental results of the fatigue life indicated that the increased testing temperature reduced the fatigue life. However, using shot peening at high temperatures increased the fatigue life by 8% when loading sequence L-H and 10% when loading sequence H-L. The results showed a satisfactory degree of safety for the present model. Nevertheless, Miner’s model featured two models: one for low–high loading and high-low loading. The results were proper for prolonging fatigue life.

Study on Calculation Method of Bending Performance of Concrete Sandwich Composite Slab.

In order to explore the flexural behavior of a concrete sandwich panel under concentrated boundary conditions, based on Kirachhoff's elastic thin plate theory in this paper, the geometric deformation, physical conditions, and equilibrium relationship of a sandwich panel are deduced by constructing the layered analysis model of the sandwich panel, the basic differential equation of the flexural deformation of the concrete sandwich thin plate is obtained, and the mathematical expression of the internal force and displacement under the boundary condition of concentrated support is given. Combined with an engineering example, the proposed calculation method is verified. The results show that, in the arrangement of reliable connectors for concrete sandwich panels, the concrete wythes bear the load while the contribution of the core layer to the bending capacity of the structure can be ignored. When subjected to a laterally distributed load, the sandwich panel mainly experiences out-of-plane bending deformation, and the bending normal stress in the concrete panel layer shows a linear non-uniform distribution along the thickness direction of the panel. The bending deformation performance and bearing efficiency of a concrete sandwich slab with the change in concentrated support position have significant effects, and the load transfer efficiency can be improved by optimizing the arrangement of supports. Except for small local areas near the supports, the bending stress distribution and deformation behavior of the concrete sandwich panel can be accurately analyzed by the calculation method established in this paper.

Dynamic behaviours of rack vehicle-track system considering rack flexibility under gear-rack mesh impact

ABSTRACT There are complex and large gradients for the rack vehicle running on the large mountain slope line. Under such a circumstance, the driving gear-rack interactions will be more intensified and could induce the larger tooth bending stress of the rack. At present, the dynamics modelling of the rack in the existing literature is generally treated as a rigid body or an infinite beam model, however, which is inconsistent with reality. To accurately simulate the vibration characteristics and bending stress of the rack structure, it is necessary to establish a detailed dynamic model considering the flexibility of the rack structure. In this study, the free beam and rod models are, respectively, used to describe the vertical and longitudinal flexibilities of the rack with the finite length. Then, the proposed rack dynamics model is introduced into a rack vehicle-track coupled system, and the developed dynamics model is validated by comparing the results from the simulation with the tested data. Finally, the vibration and bending stress features of the driving gear-rack engagement are analysed under different mounting deviations. The simulated results can give theoretical references for the design and structure optimization of the rack track structure.

Performance reliability evaluation of high‐pressure internal gear pump

AbstractWith the development of the high‐end equipment technology, the performance requirements of the internal gear pump (IGP) under high pressure are also increasing. However, the increase of working pressure will lead to the instability of gear pump performance in terms of volumetric efficiency, noise, reliability and so on, it is necessary to reasonably evaluate the reliability level of high‐pressure IGP. The reliability analysis of the high‐pressure IGP is carried out from the aspects of flow, noise, and gear strength in this paper. First, the output flow rate and far‐field flow‐induced noise of the high‐pressure IGP were obtained through fluid numerical simulation, and experimental verification was conducted. Then, based on the time‐varying meshing stiffness, backlash function and static transmission error of the gear pair, a nonlinear dynamic model of the internal meshing gear pair was established. The time‐varying meshing force was obtained through the dynamic model of the gear pair, and then the tooth contact stress and tooth root bending stress were obtained. Finally, considering the uncertain factors affecting the performance of the high‐pressure IGP, Latin hypercube sampling (LHS) combined with dendrite network (DD) was used for random response modeling. The performance reliability of the high‐pressure IGP, including output flow rate, far‐field flow‐induced noise, and the strength of gear pair, were estimated based on the fourth moment‐based saddlepoint approximation (FMSA). The reliability analysis results can provide a theoretical basis for the structural optimization design of the high‐pressure IGP.

Degree of bending of FRP-reinforced tubular X-joints in offshore jacket-type structures under in-plane bending moment

In offshore jacket structures, the stress within the chord thickness of tubular joints arises from both membrane and bending stresses. The Degree of Bending (DoB)—the ratio of bending stress to the total stress—is key to evaluating these joints' fatigue resistance. This study delves into the DoB in tubular X-joints reinforced with fiber-reinforced polymer (FRP) subjected to in-plane bending moment. It begins by validating finite element (FE) analysis accuracy through comparison with existing theoretical and experimental evidence. Following this, the analysis of 166 joints was conducted to examine how variations in FRP characteristics (such as type, layer count, and layout) and the joints' dimensionless geometric factors influence the DoB and its ratio in reinforced joints compared to their unreinforced counterparts. Findings indicate that FRP layers enhance fatigue resistance by lowering hot spot stresses on the chord's inner and outer surfaces and elevating the DoB value by up to 26.16%. Consequently, the study introduces a parametric formula for calculating the DoB in FRP-reinforced tubular X-joints under an in-plane bending moment. This development is significant, as there was no existing parametric formula for determining DoB in FRP-reinforced joints. The proposed formula stands out for its high determination coefficient and minimal error, effectively addressing a notable gap in the field.

Probabilistic Weibull reliability of a shaft design subjected to bending and torsion stress

The circular shaft serves as the axis of rotation for the components. It is subjected to flexion and tearing, indicating that fatigue is the mode of failure. The range of stresses resulting from the mean and alternating loads determines the occurrence of fatigue failure. The deterministic fatigue analysis, calculated using the stress average obtained from SN curves, can only represent the mean life. This is because the stress range is not a single number, and therefore it cannot provide the reliability level for the stress. The study employs the Weibull distribution to estimate loads and parameters for a probabilistic shaft design under bending and torsion. The minimum strength is assessed using corresponding stress analysis to determine the reliability index for the designed shaft.

Evaluating the Impact of Environmental and Operational Conditions on the Characteristics of CFRP Epoxy Composites

The purpose of this study is to determine the material properties of CFRP composites in the form of a fabric for the construction of racing car bodywork. This work focused on the determination of the strength and tribological properties as well as investigating the effects of the operating environment on the developed material. Three material variants, differing in the number of layers used to produce the reinforcement, were used in this study. The tests were carried out on two-/three-/four-layer sheets produced by infusion. Due to the later use of the tested composites for the sheathing of a racing car, the results obtained were analysed in terms of the most favourable strength properties while keeping the weight as low as possible. In this study, the hardness, impact strength, and tensile and bending stresses of the developed composites were examined. In addition to the strength properties, the density, the effects of immersion in water, and the composite’s resistance to staining and friction in the presence of aggressive media were also checked. The structure and the breakthroughs resulting from the strength tests were observed using a stereoscopic microscope. The material’s resistance to sunlight and UVB was also tested.

Fabrication and Characterization of Baobab Pod (Adansoniadigitata) FiberReinforced Polyester Resin Composite

Baobab pod fibres were obtained from Sabo market in Zaria and sliced longitudinally, screened out from the baobab fruit, washed with water, dried under sun for fabrication and characterization. The fiber was extracted and treated with 5% NaOH solution. Important samples were fabricated with different fiber loading of 10wt%-30wt%. The samples were moulded using Hand Lay-up method followed by pressing and post cured at 60oC for 3 hours. The result showed tensile strength decreases as the loading of fiber increased from 20 wt% to 30 wt%. It was also observed that baobab composite has the highest tensile strength of 18.85 MPa at 20 wt% and least (16.45 MPa) at 15 wt%. The result also revealed the elongation at break increased from 20 wt% to 25 wt%. At 25wt% it has a maximum value (18.4%) elongation at break; at 30wt%. It was also observed that the density increased with increase in the fiber loading from 15wt% to 30wt% (1.23g/cm3 - 2g/cm3) respectively. At 15wt% shows a maximum water take-up of 6.53% while from 20 wt% to 30 wt%, Flexural strength increased from 10 wt% to 15 wt% (23.98MPa - 46.3Mpa). However, the bending stress decreases on increasing the fiber loading from 20-30 wt% (30.2 Mpa – 25.2 Mpa). The elastic nature of the composite generally increases with increased in fiber loading. This study, however recommend hybridization of baobab pod fiber with other natural fiber to investigate the mechanical and physical property of the hybrid composite for better result.

Researching on the Effect of Input Parameters on the Quality and Manufacturability of 3D-Printed Cellular Samples from Nylon 12 CF in Synergy with Testing Their Behavior in Bending.

The study of cellular structures and their properties represents big potential for their future applications in real practice. The article aims to study the effect of input parameters on the quality and manufacturability of cellular samples 3D-printed from Nylon 12 CF in synergy with testing their bending behavior. Three types of structures (Schwarz Diamond, Shoen Gyroid, and Schwarz Primitive) were selected for investigation that were made via the fused deposition modeling technique. As part of the research focused on the settings of input parameters in terms of the quality and manufacturability of the samples, input parameters such as volume fraction, temperature of the working space, filament feeding method and positioning of the sample on the printing pad were specified for the combination of the used material and 3D printer. During the experimental investigation of the bending properties of the samples, a three-point bending test was performed. The dependences of force on deflection were mathematically described and the amount of absorbed energy and ductility were evaluated. The results show that among the investigated structures, the Schwarz Diamond structure appears to be the most suitable for bending stress applications.

Almond shell particle containing particleboard mechanical and physical properties

A significant byproduct of almond fruit industry, hard almond shells, was considered as a supplement material in particleboards for contributing to the circular economy goal with a higher added value product. The envisioned particle boards were not only for furniture but also construction regarding insulation. Accordingly, industry unspecific boards were produced. Almond shells were obtained from industry and ground into particles ranging from 0.4 to 3.4 mm. Those particles were mixed with black pine particles in different mass ratios to produce particleboards. The production included chemical and physical processes. Generated particleboards were subjected to specific physical and mechanical tests. Physical properties, such as density, thickness swelling, and water absorption, were determined. Mechanical properties, including deflection, elasticity modulus, bending stress, and maximum force before failure values were also measured and calculated. Boards with different densities were subjected to same mechanical and physical tests. The results show that an increase in almond shell particle amount in the particleboard makes the board more brittle and rigid. The physical tests show less thickness swelling and water absorption with increasing amount of almond shell particles. Therefore, almond shell particles may be more favorable for indoor decoration or insulation instead of furniture. Board density has a marginal effect on mechanical behavior, and it should be one of the determinant factors for feasibility of the boards in different utilization scenarios.

Effects of radial bending stress on hot corrosion behaviour of dissimilar martensitic heat-resistant steel weldments in ultra-supercritical unit

The influences of the applied radial bending stresses on the corrosion behaviour of dissimilar weldments of two types of martensitic heat-resistant steel (F92/Co3W2) are investigated with NaCl–Na2SO4 deposited salts at 620 °C and 24 h employing a four-point bending jig. The applied external stress exhibits no obvious influence on corrosion products, which mainly consist of Fe2O3, Fe3O4, and FeCr2O4. However, the stress tends to aggravate the corrosion degree, and the weldments with stress addition yield more mass gain and greater corrosion scale thickness. Such phenomenon is more serious in the parent F92, implying F92 is more sensitive to the corrosion environment with stress. The corrosion scale of weldments without stress shows typical double-layer structure: outer Fe–O layer and inner Fe–Cr–O layer, while the weldments with bending stresses show interesting multi-layers (10 or more layers) with Fe-oxide and Fe, Cr-oxide alternately appearing. The mechanism for hot corrosion behaviour and the influence of hot corrosion on the local mechanical properties of different welding zones with and without stresses are further discussed.

Residual Stress Determination with the Hole-Drilling Method on FDM 3D-Printed Precurved Specimen through Digital Image Correlation

The hole-drilling method (HDM) is a common technique used for the determination of residual stresses, especially for metal alloy components, though also for polymers. This technique is usually implemented with strain gages, though other methods for determining the fields of displacements are quite mature, such as the use of digital image correlation (DIC). In the present paper, this combined methodology is applied to a 3D-printed PLA precurved specimen that is flattened in order to impose a bending distribution which can be considered known with a reasonable accuracy. The back-calculated stress distribution is in agreement with the expected (imposed) bending stress, however, a converging iterative procedure for obtaining the solution is introduced and discussed in the paper.

Protein content and antioxidant enzymes activity in reaction wood of poplar and their response to different levels of sustained bending stress

Protein content and antioxidant enzymes activity in reaction wood of poplar and their response to different levels of sustained bending stress

Hybridization of woven kenaf and unidirectional glass fibre roving for unsaturated polyester composite

This is a study on the mechanical properties of kenaf/glass-reinforced polyester composites intended for use in structural profiles with a wall thickness by max. 6 mm. Mechanical properties such as tensile, compression, bending and interlaminar shear stress were investigated by comparing the hybrid variants with the pure fibreglass variant. According to the study, woven kenaf/unidirectional glass roving (WK/UG) alternate recorded the highest tensile properties among hybrid samples. It demonstrated a decrement of about 8.2% of the tensile strength (404.54 MPa) and 10.7% of tensile modulus (24.54 GPa) compared to conventional fibreglass samples. Alternating WK/UG samples demonstrated higher compressive strength (417.15 MPa) compared to other hybrid specimens, recording a slight decrease at 6.09% compared to pure fibreglass composites. The highest bending properties were also observed in hybrid alternate WK/UG samples among other hybrid laminates with only a decrement of 4.13% in modulus of rupture (456.33 MPa) and 1.9% in modulus of elasticity (14.49 GPa) when compared to the control specimen. The ILSS of hybrid composites 2WK/3UG/2WK (30.97 MPa) and WK/UG alternate (34.90 MPa) showed good agreement with the pure fibreglass (42.33 MPa) composites. Using SEM images, tensile fractured specimens were examined to comprehend composites’ failure mechanism and interfacial adhesion. Overall, woven kenaf/unidirectional glass roving alternate sequence is chosen as a potential alternative in developing structural profiles for moderate load-bearing structural applications. In contrast, 3WK/UG/3WK with a higher kenaf to glass ratio demonstrate potential in low load-bearing structural profile applications.Graphical abstract

Optimization of polyoxymethylene spur gear pair using meta-heuristic algorithms: A comparative study

Design-optimization of power transmitted elements such as gears is a complicated process to accomplish as the mathematical model acquires to be in compliance with the optimization algorithm used. Utilization of technical standards and handbooks assisted engineers and designers with designing the gears, however the results were inefficient, thus meta-heuristic algorithms were approved for optimization, for example, genetic algorithm. In this paper, optimization of single stage spur gear pair made of polyoxymethylene material was carried out using genetic algorithm (GA), artificial bee colony (ABC), JAYA, grey wolf optimizer (GWO), and whale optimization algorithm (WOA) in MATLAB. Three single functions were used as objectives, those are, weight, power loss, and center distance. Module ( m), face width ( b), number of pinion teeth ( z1), and finally profile shifts ( x1, x2) served as design variables. Unlike steel gears which were constrained by handling root bending stress and flank pressure, more constraints were added to the problem with the increase of complexity such as root and flank temperature, tooth deformation, and wear abrasion. The results showed a significant decrease in all three objectives when optimizing each objective solely with variation of the variables. It is also observed that JAYA has the superiority in decreasing the three objectives in comparison to GA and ABC nevertheless, in agreement with GWO, and WOA.

MODELLING AND 3D PRINTING OF JCB ARM

The Hydraulic excavator machines are heavy duty earth movers consisting of a boom, arm and bucket. It works on principle of hydraulic fluid with hydraulic cylinder and hydraulic motors. The Hydraulic excavator arm operation require coordinated movement of boom, arm and bucket. The important criteria for the design to be safe is that, the digging forces developed by actuators must be greater than that of the resistive forces offered by the surface to be excavated. The main objective of this paper is to perform design and analysis Excavator Arm for the calculated Force. The CATIA software is used for making the 3D model of the excavator arm linkage. By using ANSYS workbench software analysis of the excavator arm is done at existing digging force and lifting force. Excavator bucket is very crucial element of hydraulic excavator. The whole loads of excavated materials have been carried out by this element. As the present mechanism used in excavator arm is subjected to deformation and bending stresses during lifting and digging operation respectively, because of which failure occurs frequently at the bucket end of the arm. Keywords: Excavator arm, Digging force, CATIA, ANSYS 16.0.

Multi-objective design optimization of polymer spur gears using a hybrid approach

Polymer gears are used in applications requiring small to moderate loads to effectively transmit power and use the limited place available as possible. Various commercial standards have been provided designers with the rating criteria and acquaintance of different polymer material properties for the process of design. However, the result was unsatisfactory in terms of economy, time, and the optimality of the product. Thus, classic and stochastic algorithms have been embraced to reach the best design of polymer gears. Taking advantage of the former and latter algorithm’ methods, optimal design of gears could be attained with an increased gear life span and decreased failure modes. In this study, polyoxymethylene (POM) spur gear set has been optimized combining the mathematical model from plastic standards and hybrid optimization approach of multi-objective genetic algorithm (MOGA) and sequential quadratic programming (SQP). Weight and power loss were the objective functions. Five design variables were optimized with the satisfaction of bending and contact stresses, temperature, wear, and deformation as constraints. Solutions of the problem were formulated as Pareto optimal set. The results of multi-objective were compared with previously published single-objective optimization. The results favored multi-objective optimization (82.67%, 31.39% reduction in weight and power loss respectively) as it gave the best applicable solution fitting in real life situations. The results also went hand in hand with literature confirming the efficiency of the proposed algorithm. With the variation of operating parameters, various optimal designs could be obtained where the designers can choose the design that is suitable for a particular application.

Mechanical Characterization Potentials of Aluminide Diffusion Coatings on Molybdenum Substrates

A mechanical test strategy is designed to determine the resistance of protective intermetallic aluminum layers on molybdenum substrates. Performing mechanical experiments, such as compression, four‐point bending and indentation tests, the specific failure behavior and a potential impact of observed phase transformations within the interface zone on the structural integrity and adhesion strength are examined. Herein, the applied test structure aims at the description of damage characteristics and critical deformation states regarding the type of loading. In this respect, it focuses on delamination behavior under compressive load and crack channeling due to bending stress. The analysis of the mechanical experiments is supported by various measurement techniques, including 3D camera equipment (GOM) and an acoustic emission (AE) analysis system. In particular, the application of the AE technique in this work provides a helpful contribution to the detection of delamination failure and the development of multiple crack channeling. Considering the successfully applied experimental approaches, it is assumed that more complex coating‐base material combinations can be characterized this way with respect to preceding annealing effects and the thereby influenced load capacity of thin films under different loading types.

THE METHOD OF SELECTING THE MOST APPROPRIATE MODIFICATION OF THE MECHANISM USING COMPUTER TECHNOLOGIES

The article presents a method for identifying the most appropriate modification of the mechanism with the required output shaft rotation frequency by constructing various geometric models and calculation schemes. This technique based on the design and analysis of modification of the vibration stand mechanism for testing measuring equipment and products for vibration resistance and vibration resistance. The strength analysis of contact stresses and bending stresses in the engagement zone of the elements under various external and boundary conditions was performed using analytical and computer methods. A 3D geometric model of the parts is being created with the display of traces of operation on the surface of the parts, anticorrosion coatings, using materials of various heat treatment in the Compass 3D V.21 package. The most appropriate modification of the mechanism is identified by analyzing the distributions of maximum equivalent stresses according to Mises, the main stresses according to geometric models of parts. If these stresses exceed the limit values or the mechanism is underloaded, the geometric dimensions of the transmission parts should be changed, another material for the transmission parts should be selected and the strength calculations should be repeated.

Finite Element Analysis of Spur Gear Set in Noodles-making Machine Using Different Materials and Face Widths

This paper focuses on the design and structural analysis of a spur gear set for a noodles-making machine by changing three different materials (ASTM A 536, ASTM A 220, and AISI 1020) and gear face widths. Gear corrosion occurs at contact points as a result of bending stress and contact stress. This is the major source of the gear failure of the noodles-making machine. Pitch diameters of 50mm and modules of 5mm spur gears are selected in the design of the roller gear set. In theoretical analysis, the AGMA contact stress equation was used based on the Hertzian theory. The minimum von Mises stress and effective strain are found on AISI 1020 carbon steel by using ANSYS 17.0 software. In this paper, von Mises stress and effective strain are analyzed by changing the face widths of spur gear set to 8mm, 10mm, 12mm, 14 mm, and 16mm and using finite element analysis (FEA). Although all face widths are safe for this design, 12mm is chosen in this paper due to power consumption and strength points of view.