The transient vibration analyses of optimised Fibre Metal Laminates Cylindrical shells were examined in this paper. One of the most innovative aspects of this study is identifying an applied trend for optimizing the FML cylindrical shell construction to achieve maximum reliability. The FML shell reliability is determined using the First Order Reliability Method (FORM) and the Hashin failure criteria. To achieve this objective, the Shell is constantly subjected to a static load, and the resulting tensions within the FML layers of the shell are measured. The maximum tension is determined using the Hashin method, and the stability of the shell is subsequently estimated. Next, the amounts of reliability are certified according to shell stability. To maximize the FML shell reliability, the sequence of the composite-metal layers and fibre orientation are often modified, and for each case, the sample reliability is calculated. The second section of this study examines the effect of the optimized structure of the FML shells on the acceleration and displacement of these shells under dynamic loading. The energy approach is used to obtain the Equations of motion, whereas the mode superposition method is employed for transient vibration analysis.
Mechanical filtration of solid and liquid phases with the help of a centrifuge mechanism is a common operation in industries, particularly for salt dehydration. The process is mainly based on the centrifuge action between particles and fluids. Currently, most of the studies have been performed on single-stage centrifuges while there it is required to know and analyze the behavior of the multi-stage pusher centrifuges in order to optimize their efficiency. The structure and dynamic performance of the two-stage pusher centrifuge device have been analyzed in the current study in three phases: modal, particle behavior, and transient state dynamics analysis. The results of the modal analysis have demonstrated that the safety margin obtained in the context of the resonance occurrence for the internal basket set and subset due to linear and rotational inertial forces has been . Based on the results of the transient dynamics analysis, the stability of the particle behavior has been about or of the particle feeding time, the maximum displacement at the critical point of the inner basket subset has been , and the critical stress value has been about ; which has been acceptable in terms of mechanical strength of the assembly versus the stresses and strains caused by the operation of the device. Thus, it is recommended based on the results to maintain the maximum rotational motion (36.68 rad/s) and no significant change in the particle feeding rate compared to the specified value (0.56 kg/s).
Diaphragm bellows are one of the essential parts in sealings and rotary equipment which are affected by their design parameters. This paper investigated the effect of weld length and plate thickness, on the mechanical characterization of diaphragm bellows. The mechanical characterization includes stress distribution, bellows deflection, spring constant, and fatigue life of the welded metal bellows. Finite element analysis was employed to study the effect of weld length and sheet thickness on the diaphragm bellows. In this regard, 12 models were designed based on experimental parameters. The number and combination of tests were designed by the response surface method and the results were evaluated by ANOVA analysis. According to the results, if weld length and sheet thickness increase, the maximum stress and deflection of the bellows decrease, and the spring constant increases. The effect of sheet thickness on the behavior of the bellows is greater than weld length and it creates a limitation due to the effect on the spring constant. In the acceptable ranges of weld length and sheet thickness, based on fatigue analysis, the maximum life cycle is 1.2×106 and the minimum life cycle is 1.7×103.
Writing on steel coils and slabs (to mark them) is one of the problems faced by domestic steelmaking industries. Currently, this operation is done with the help of human power, which has its own drawbacks. In order to solve these problems, a marker robot is supposed to be applied. This robot writes letters, numbers, and signs on steel coils with an automatic paint spray gun. The robot intended for this purpose is a 5 degrees of freedom robot (5DOF), 3 degrees of freedom are related to the robot arm, and the other 2 degrees are related to the robot wrist. Due to the special conditions governing the problem, the solution of inverse kinematics has been done by the geometric method, which is simpler than the algebraic method. In order to determine the path of the robot (the path of letters and numbers), a series of time-dependent Equations have been applied. To show the accuracy of the planned trajectory, simulations have been carried out on the mentioned robot and the movement trajectory of the end-effector and the configuration of the arm have been graphically displayed. The programming of the robot's trajectory has been performed in MATLAB and LabVIEW and Visual Nastran has been applied to simulate the robot's trajectory.
Lattice structures have garnered significant interest across various sectors due to their unique characteristics, such as a high strength-to-weight ratio and a high damping coefficient. In addition, honeycomb structures necessitate a zero Poisson's ratio to prevent unnecessary stress and strain. To address this issue, a cellular honeycomb core that incorporates in-plane corrugated U-shaped beams with close-to-zero Poisson's ratio was proposed. This research assesses a method to increase the capacity of structure to absorb energy. To achieve this goal, a circular cylinder was utilized to improve the mechanical properties. The compressive characteristics of the modified structure were analyzed and compared to the conventional structure. The objective of this study was to boost the energy absorption capabilities of the conventional structure while maintaining the Poisson's ratio.
Nowadays, various methods are being developed for new composites and nanocomposite compounds. Investigating the properties of nanocomposites and finding their optimal properties can enhance their utility. In this study, the mechanical molecular dynamics method was initially utilized to investigate the mechanical properties of an aluminum/carbon (Al/C) nanocomposite. Subsequently, the effect of temperature change, strain rate, and carbon content on the nanocomposite's elastic modulus and ultimate strength were investigated. To simultaneously investigate these three parameters and identify the optimal point for the elastic modulus and ultimate strength the experimental design method for optimization was utilized. The Derringer method was utilized to determine the optimal parameters for the simultaneous optimization of two response variables, i.e., elastic modulus and ultimate strength. The findings reveal that the optimal conditions occur simultaneously at 300 K, strain rate 0.01, and carbon content of 2 %, with an elastic modulus value of 51.046 GPa and an ultimate strength value of 5.1117 GPa. Then, the verification of the proposed optimal condition has been completely done via molecular dynamics simulation.
With the growing integration of nanotechnology into everyday life and the importance of nanoelectromechanical systems, this article examines the non-linear free vibrations of an Euler-Bernoulli (EB) composite beam reinforced with graphene nanoplatelets (GN), considering the Non-Local Strain Gradient Theory (NLSGT). First, the elastic properties of the nanocomposite reinforced with GN were calculated using the rules of mixtures and the Halpin-Tsai (HT) model. Then, the Equations describing the motion for the EB beam were obtained through the virtual work law, the NLSGT, and the von Kármán (VK) strain field, and were analyzed through the homotopy technique. After solving the Equations, the obtained results were compared with those available in other sources, showing a very good agreement. Finally, the outcomes of varying the graphene plates (GPLs) weight fraction, the GPLs distribution, and the proportional ratio of length to thickness of the beam regarding the non-linear natural frequency (NF) were investigated where one of the important results of this paper is that the highest non-linear NF occurs first in the X-GPLRC distribution, then in the A-GPLRC distribution, and finally in the O-GPLRC distribution.
In this research, the application of the homotopy perturbation method to solve nonlinear Equations arising in oscillatory systems is investigated. In this way, the performance of the Homotopy Perturbation Method (HPM) is compared with the numerical methods to find the solutions of nonlinear Equations in the vibration field. To this end, the Duffing–Holmes oscillatory model with nonlinear terms is regarded and solved by the HPM method. In order to validate the obtained solution by the HPM, the answers are compared with those of numerical methods. The results clearly depict that the homotopy perturbation method, without needing to small parameters, could present the answers near to the exact solutions and also to the numerical one.
In this study, the development of a generative algorithm related to the lattice conical shell (Isogrid pattern) and the modeling of the stiffened shell under mechanical and thermal loads are discussed. An algorithm has been developed for the lattice conical shell (MATLAB software), which generates the pattern of stiffeners on the conical shell. Modeling of the lattice conical shell is done in SolidWorks software. The structure of stiffened shell is analyzed under loading using the Finite Element Method (FEM) in the ANSYS Workbench. The modeling of the lattice conical shell is investigated under mechanical (axial and bending load and internal pressure) and thermal loads. It is concluded that the stiffeners can resist buckling and mechanical failure under mechanical and thermal loading conditions, while the mass is significantly reduced. This shell can be used in various industries due to its lightweight and high resistance. Whereas the safety factor of the final model is about 2 and the model is acceptable for desirable internal pressure (0.6 MPa), the total system mass is about 41 kg.
Currently, manufacturing and repairing industrial equipment in a short time with the least cost has been a challenge. Furthermore, the idle time of the industrial machines due to their failed parts imposes high losses on the production process. Applying 3D printers to manufacture damaged parts quickly is a promising measure to tackle the abovementioned problem. This article is an efficient approach to the manufacture and analysis of a universal joint (U-joint) as the case study with Polylactic acid (PLA) and Acrylonitrile butadiene styrene (ABS) through the 3D printing process. U-joints are widely used as a coupling in industrial equipment to alleviate the misalignment of input and output shafts in many gearboxes and pumps. Because of undergoing fatigue loads, the failure occurrence in U-joints is very probable. Therefore, an attempt is made here to substitute this part with a 3D-printed one. Besides, comparing and evaluating the results of FEM simulations for the sake of selecting the most suitable material for the U-joint are done. According to the FEM results, the maximum stress imposed on the U-joint was obtained 28.8MPa which is lower than the yield strength of both PLA and ABS materials; however, the results show that PLA has higher fatigue strength than ABS in this case.
The burnishing process showcases a novel approach for significantly improving the surface quality and hardness of metals, particularly aluminium, copper, and brass. This paper presents a novel approach to optimize the burnishing process of Aluminium 2024 by simultaneously analyzing the effects of spindle speed, feed rate, and burnishing force, a comprehensive method that has not been addressed in prior studies. Utilizing a specially designed roller-based tool with a lathe machine, we systematically varied key parameters—spindle speed, feed rate, and burnishing force—through a full factorial design with two repetitions. Advanced statistical analysis was conducted using Minitab software to assess the effects of these parameters on surface roughness and hardness, employing regression methods for precise predictions. Remarkably, the results demonstrated that optimal surface roughness (Ra = 0.05 μm) was attained at a feed rate of 0.11 mm/rev, spindle speed of 1000 r/min, and burnishing force of 1000 N. This research not only highlights the effectiveness of the burnishing process in enhancing the mechanical properties of aluminium alloys but also introduces innovative methodologies that pave the way for improved industrial applications. Future studies will investigate the effects of burnishing in corrosive environments and its impact on material strength.
In this research, a modern method for making foam patterns, which is one of the most important steps of casting with a lost foam pattern, has been used. A semi-automatic hot wire machine was built to cut and create foam patterns. Two types of foam patterns were prepared by manual method and cutting method with semi-automatic machine. The sizes of the obtained foam patterns were evaluated and the accuracy of each method in the production of foam patterns was compared. According to the density of the foam used in the experiments, the volume of the prepared patterns was obtained by manual and semi-automatic methods. The additional volume in the prepared patterns was calculated by both methods. The amount of economic losses caused by excess volumes was investigated. The results of the research determined that the accuracy of the sizes of the patterns prepared by the semi-automatic method was more than twice the accuracy of the patterns prepared by the manual method. The patterns prepared by the semi-automatic method had an additional volume of 1.9% compared to the volume of the original part. While the mentioned amount for foam patterns cut by the manual method was 9%. Therefore, the economic efficiency of casting parts using foam patterns made by semi-automatic method in terms of melting consumption for aluminum parts was 8% more than production parts using foam patterns made by manual method.
Sports equipment is widely available in the international market. The market's focus is on the design of sports equipment to prevent injury, and all equipment must be designed to enable performance without causing injury. The purpose of this study is to design and manufacture a new volleyball and comparison of kinetic components with other volleyballs. The present study is applied and developmental type. We used four full-size Federation International Volleyball (FIVB), official volleyballs (V200W MIKASA made in Japan, FOX volleyball, model Spain, made in the United States, BETA, and new volleyballs made in Iran) to determine the biomechanical components, such as stiffness and Ground Reaction Force (GRF) on that ball. Ground reaction force variables and stiffness of all samples were recorded by a force plate device (sampling rate: 1000 Hz) and Shore C (Newton’s per meter N/m), respectively. There was a significant difference in all groups between stiffness (P<0.001), vertical ground reaction force (vGRF) (P<0.001), and impulse (P=0.012), also the LSD Post Hoc test showed that stiffness, vGRF, and impulse in new volleyball and MIKASA volleyball were less than BETA and FOX volleyballs. The results indicate that the biomechanical components of the new volleyball with MIKASA were similar. Therefore, the new volleyball design appears to be suitable for an official competition. Nonetheless, more clinical studies are needed to evaluate the kinetic and kinematic parameters of using new volleyball.
The Reinforcement Learning Approach (RL) is used to solve the path-planning problem of an autonomous mobile robot in unknown environments. Despite that RL is a recent and powerful tool, it requires a lot of training processes because there are so many parameters in the agent’s training process. Some of these parameters have a larger effect on the convergence of the learning process than others, so, knowing these parameters and their suitable values makes the training process more efficient, saves time, and consequently makes the trained agent execute the required task successfully. No analytical equations are available to determine the best values for these parameters, therefore, in this paper, a statistical analysis is made using the design and analysis of experiment (DoE) methods to determine the parameters that have the largest effect on the training process. After that, analysis is done to determine the values of the most effective parameters. Results show that the determined parameters lead to a successful autonomous path planning in different unknown environments
Industrial heaters play a pivotal role in various processes in industries and consume significant energy resources. Increasing the energy efficiency of these heaters is of great importance in the current energy-saving scenario. This study improves existing heaters by introducing an additional convective section, using the power of computational fluid dynamics to optimize heat transfer and improve overall efficiency. This paper presents a comprehensive study on upgrading existing heaters by incorporating an additional convection section, facilitated by a thermal and computational study. The main focus is on increasing the efficiency of conventional heaters by optimizing the heat transfer process through the newly added convection section. This paper describes the methodology used to analyze, model, and simulate the reinforced system, presents the results generated by CFD, and discusses the implications of the findings on the overall efficiency of the heaters. In this regard, to study and design the optimal mode of energy saving and complying with the conditions of optimal operational performance, various plans are examined and the best method is selected for heater optimization.
Trajectory planning in cable-driven robots is more challenging than rigid-link ones. To maintain the robot control, the cable tensions must be positive during motion. This paper presents a direct collocation approach to solve the optimal trajectory planning based on the minimization of a robot's tension and tension-rate objective functions. Besides, during robot motion, the cables must be tensile. The configuration of a cable parallel robot composed of a 3-cable and a prismatic actuator neutralizes the moving platform’s weight while improving tensionability. To generate smooth trajectories, the proposed method is compared with two standard approaches: GPOPS-II software package which uses Legendre-Gauss-Radu quadrature orthogonal collocation polynomials and direct collocation by using B-spline interpolation curves. Despite the efficiency of using B-spline functions in trajectory planning, numerical simulations demonstrate that the Hermite-Simpson direct collocation approach has a substantial benefit in the computation cost and accuracy for trajectory planning of a cable-driven parallel robot. Also, by choosing appropriate constraints and cost functions, the cable forces in the parallel robot can be well managed.
In critical manoeuvres where the maximum tire-road friction capacity is used, the vehicle's dynamic behaviour is highly nonlinear, and there are strong couplings between longitudinal and lateral dynamics. If the tire-road friction conditions change suddenly during these manoeuvres, the vehicle control will be very complicated. The innovation of this research is a control algorithm to manage vehicles on a curved path with sudden tire-road friction change. The main advantage of the proposed controller is that it is robust to the change of the friction coefficient and other unmodeled uncertainties and ensures vehicle stability with low computational volume. The evaluation of the proposed adaptive controller has been done using the full vehicle model in CarSim software and by defining three different manoeuvres, moving at a constant speed on a curved road, lane-change, and lane-change with braking. Also, in the obtained results, the noise of the yaw speed signals and longitudinal and lateral accelerations are considered. The estimation of the longitudinal and lateral velocities is also done using these data. The obtained results showed that the proposed integrated control can manage the highly nonlinear dynamics of the vehicle in the existence of a sudden and significant change in the friction coefficient.
In machining processes, the self-excited vibration between the cutting tool and the workpiece is an important issue that can result in undesirable effects, for example, poor quality of the final surface, low dimensional accuracy, breakage of the tool, and excessive noise. To anticipate this problem, statistical features of the vibration signal, such as mean, variance, and standard deviation, have been extracted from online measurements. The synthesis criterion (SC), which is based on the standard deviation (STD) and the one-step autocorrelation function (OSAF), has been employed to detect quickly the threshold of chatter vibration. In this article, flexible workpieces with varying cutting depths have been selected to detect online chatter vibrations during milling operations. In order to collect an analog vibration signal, an STM32 card has been selected with a sampling rate up to 20 kSPS. A high-bandwidth, lightweight film piezoelectric sensor is attached to the workpiece. Unlike other sensors, such as load cells or acceleration sensors, the film piezoelectric sensors do not alter the dynamics of the system. In this research, cost-effective hardware is also developed to capture vibration signals reliably and efficiently. The experimental results confirm that the developed SC algorithm can efficiently predict the onset of chatter vibration as it was able to detect the onset of chatter vibrations within 0.18 sec. Thus, the SC algorithm can considerably enhance the milling operations of flexible parts.
Second-order corrugated cores are one type of hierarchical cores that use the common corrugated cores as constituent elements for the main core. This paper attempts to identify and optimize the bending properties of composite sandwich panels with second-order corrugated core. To this end, both first- and second-order corrugated cores are constructed and force-displacement diagrams are extracted in three-point bending tests. Finite element models are created and the deflection results are validated by experiments. Based on the Taguchi method, various finite element models with different geometrical parameters are modeled and reaction force and stiffness are determined. Stiffness formulas for first- and second-order corrugated cores are determined by using regression analysis. The constrained-optimization results are determined to optimize the stiffness of sandwich panels with first- and second-order corrugated cores, separately. The global optimization problem is implemented to compare the first- and second-order configurations.
The disordered fibrous networks provide load-bearing and main structural to different biological materials such as soft tissues. These networks display a highly nonlinear stress-strain relationship behavior when subjected to mechanical loads. This nonlinear strain-stiffening behavior is dependent on the network microstructure and properties of constituting fiber. We conduct a comprehensive computational study to characterize the importance of material properties of individual fibers as well as the local connectivity or coordination number and bending rigidity in the overall nonlinear mechanical response of a 3D random fiber network. The presented model shows the nonlinear stiffening with increasing applied shear strain more than critical shear strain. We determine the amount of strain-stiffening as a function of network microstructure parameters and the amount of nonlinearity of the fibers. The results show that the constitutive behavior of fibers displays much more strain-stiffening than networks made up of linear fibers. We find that the importance of the nonlinear reaction of individual fiber materials in the general mechanical behavior of networks becomes more important with increasing network connectivity. Furthermore, the amount of stress created in the network under shear increases with the enhanced connectivity of the network due to an increase in the network stiffness. Our model points to the important role of the mechanical response of individual fiber as well as the microstructure of the network in determining the overall mechanical properties of the 3D random network, which could be used to design and better understand the complex biomimetic network systems such as biological tissues and artificial engineering networks.
