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Compared with the forward design method through the control of geometric parameters and material types, the inverse design method based on the target stress‐strain curve is helpful for the discovery of new structures. This study proposes an optimization strategy for mechanical metamaterials based on a genetic algorithm and establishes a topology optimization method for energy‐absorbing structures with the desired stress‐strain curves. A series of structural mutation algorithms and design‐domain‐independent mesh generation method are developed to improve the efficiency of finite element analysis and optimization iteration. The algorithm realizes the design of ideal energy‐absorbing structures, which are verified by additive manufacturing and experimental characterization. The error between the stress‐strain curve of the designed structure and the target curve is less than 5%, and the densification strain reaches 0.6. Furthermore, special attention is paid to passive pedestrian protection and occupant protection, and a reasonable solution is given through the design of a multiplatform energy‐absorbing structure. The proposed topology optimization framework provides a new solution path for the elastic‐plastic large deformation problem that is unable to be resolved by using classical gradient algorithms or genetic algorithms, and simplifies the design process of energy‐absorbing mechanical metamaterials. [ABSTRACT FROM AUTHOR]

The cold plate cooling system has become one of the most practical and promising Li‐ion battery thermal management systems for electric vehicles. The existing cold plate has complex structure with high production cost, and the energy consumption is relatively high. In this paper, a detailed optimization study of cavity cold plate is carried out. The heat generation data of the pouch Li‐ion batteries were obtained through experiments, and the data were applied to the finite element method simulation of the cavity cold plate thermal management system. The effects of cavity cold plate thickness (d1), cold plate inlet and outlet width (d2), and inlet coolant mass flow rate on battery temperature and cold plate pressure drop were discussed. The results showed that the optimization allowed the cavity cold plate to control the battery maximum temperature within 40°C and temperature difference within 5°C. Under the same volume of cold plates, the average pressure drop reduction rates of models where Δd (the difference between d1 and d2) is 1 mm are 65% higher than that of the models where d2 is 1 mm. This study has practical significance for improving the design efficiency of cavity cold plate. [ABSTRACT FROM AUTHOR]

Highlights • Based on the Flores contact model, we establish the dynamic model of spherical rocks vertical impact on the metal plate with the considering the energy absorbed and consumed by the compression of the rock and energy absorbed by the bending deformation of the metal plate. • Based on the Drucker–Prager criterion, we obtain the function of maximum comprehensive stress ε 0 (α, μ 1) and deduced the initial yield stress and initial yield impact velocity for the consideration of principal stress σ2. • We propose the approximate theoretical formula of the maximum contact compression of spherical rocks based on recursive solution. Influence law of impact velocity, material parameters and structure size on the dynamic response of the impact system is obtained. • The combining simulation based on ADAMS and Hypermesh was used to verify the correctness of the theoretical model. Abstract In the process of top coal caving mining, the metal sheet of the tail beam of the hydraulic support will vibrate when coal and rock particles start to impact the tail beam. In the impact between the particles and the metal plate of finite dimension, there are many complicated problems such as short duration of impact, rapid enhancement of transient stress, local large deformation of particles and macroscopic deflection of the metal plate are involved. However, the analysis of the contact force between the spherical particles and other objects is still simplified to the ideal Hertz contact problem. In order to study the real contact states of coal and rock particles impact on the metal plate, we simplified the working conditions from the coal and rock particles impact the tail beam in top coal caving mining to the system that spherical particles have similar properties to coal or rocks impact vertically on the metal plate. Based on the Flores contact theory and the energy absorbed by the bending deformation of the metal plate, the contact model of spherical rock at the compression stage was established. At the same time, we researched the initial yield stress and initial yield impact velocity of spherical rock that obeys the Drucker–Prager (D–P) criterion and proposed the approximate theoretical calculation method of maximum contact compression of spherical rocks. In the range of elastic impact velocity, the influence of impact velocity, restitution coefficient, material parameters and structure sizes on the dynamic response of the system were also analyzed. Finally, the correctness of the theoretical model has been verified by the virtual prototype simulation combined by ADAMS and Hypermesh. The research will provide the basic theory reference for the recognition technology of a single particle of coal or rock that based on the impact vibration of the tail beam. [ABSTRACT FROM AUTHOR]

Conical picks are the key cutting components used on roadheaders, and they are replaced frequently because of the bad working conditions. Picks did not meet the fatigue life when they were damaged by abrasion, so the pick fatigue life and strength are excessive. In the paper, in order to reduce the abrasion and save the materials, structure optimization was carried out. For static analysis and fatigue life prediction, the simulation program was proposed based on mathematical models to obtain the cutting resistance. Furthermore, the finite element models for static analysis and fatigue life analysis were proposed. The results indicated that fatigue life damage and strength failure of the cutting pick would never happen. Subsequently, the initial optimization model and the finite element model of picks were developed. According to the optimized results, a new type of pick was developed based on the working and installing conditions of the traditional pick. Finally, the previous analysis methods used for traditional methods were carried out again for the new type picks. The results show that new type of pick can satisfy the strength and fatigue life requirements. [ABSTRACT FROM AUTHOR]

To predict fragment separation during rock cutting, previous studies on rock cutting interactions using simulation approaches, experimental tests, and theoretical methods were considered in detail. This study used the numerical code LS-DYNA (3D) to numerically simulate fragment separation. In the simulations, a damage material model and erosion criteria were used for the base rock, and the conical pick was designated a rigid material. The conical pick moved at varying linear speeds to cut the fixed base rock. For a given linear speed of the conical pick, numerical studies were performed for various cutting depths and mechanical properties of rock. The numerical simulation results demonstrated that the cutting forces and sizes of the separated fragments increased significantly with increasing cutting depth, compressive strength, and elastic modulus of the base rock. A strong linear relationship was observed between the mean peak cutting forces obtained from the numerical, theoretical, and experimental studies with correlation coefficients of 0.698, 0.8111, 0.868, and 0.768. The simulation results also showed an exponential relationship between the specific energy and cutting depth and a linear relationship between the specific energy and compressive strength. Overall, LS-DYNA (3D) is effective and reliable for predicting the cutting performance of a conical pick. [ABSTRACT FROM AUTHOR]

Planetary gear trains are widely applied in various transmission units. Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly. Strength calculation method for planetary gear trains usually follows the method for cylindrical gears, in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely, and calculation results tend to be conservative. To overcome these shortcomings, a kinematics analysis for a planetary gear train is firstly performed, in which the influence of relative speed is investigated. Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS. Time-history curves of contact and bending stresses of sun gear, planetary gears and ring gear are respectively obtained. Also the accurate moment and its corresponding position of the maximum stress are precisely determined. Finally, calculation results of finite element method (FEM) and traditional method are compared in order to verify the effectiveness. Simulation and comparison show the stability of the proposed method in this paper. Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train. [ABSTRACT FROM AUTHOR]

• Based on the idea of reverse modeling, a finite element modeling method for CT images is proposed. • NURBS is utilized to fit complex boundary of model, which can greatly improve the finite element computational efficiency while ensuring the accuracy of the model. • The mechanical properties and failure modes of interlocked structures were studied by experiments and simulations. • The failure mode of structure is related to arrangement of pores, which can be improved by adjusting the printing strategy. Suture-inspired interlocked interfaces in nature exhibit promising industrial application potentials for advanced mechanical structures, devices and equipment. It is of significant scientific interest for studying the pull-out response and failure mode of interlocked structure as well as internal stress variations during the loading process. In this paper, finite element analysis (FEA) simulation based on X-Ray tomographic images is proposed for understanding the effects of manufacturing defects on the performances of interlocked structures, which are of critical importance for controlling the stress evolution of the interface structure and corresponding failure modes. Firstly, X-ray micro computed tomography (micro-CT) was applied for non-destructive scanning inspection of aluminum alloy additive manufacturing samples, high spatial resolution and calculation efficiency can be realized through tomographic image guided FEA scheme for generating high fidelity simulation results. Afterwards, non-uniform rational B-splines fitting method was employed for optimizing sample boundaries harvested from CT images, which allows smooth conversion from CT pixel images to high precision fitted finite element model. The B-spine fitting model can significantly improve the computational efficiency for finite element simulation without losing calculation reliability and resolution, overcoming the inherent contradictions between efficiency and resolution of the traditional pixel image finite element method. Finally, considering the mechanical contributions and interactions of external and internal porosity defects, the failure modes of the interlocked structures were further analyzed based on the results of finite element analysis. [ABSTRACT FROM AUTHOR]

A novel non-contact carrying and transportation technology is proposed based on near-field acoustic levitation (NFAL) and negative pressure adsorption effect. The disk-shaped objects can be levitated at a height of tens or even hundreds of micrometers, and a restoring force will be generated during the transportation process to make the object move toward the center of the acoustic emission plate, once the suspended object deviates from the center of the acoustic emission plate. A compact object stage is designed, and the coupling mechanism of near-field ultrasonic suspension force and hydrostatic vacuum adsorption force is revealed. The modal and harmonic response analysis of the acoustic emission unit of the object stage are carried out by using the finite element method to find the optimal operating parameters, and the impedance matching of the acoustic emission unit is carried out to improve the energy conversion efficiency. A prototype of the object stage is fabricated and assembled to verify the working performance. Ultimately, the experimental test environment is built to investigate the characteristics of the non-contact carrying and transportation system. The experimental results show that the acoustic emission unit produces the "N"-shaped ideal mode at the resonant frequency of 20190 Hz with the maximum vibration amplitude of 14.6 µm. The maximum bearing weight of the object stage is 470 g. The restoring force of the non-contact transportation system can reach 2.03 mN, which is 120.65% higher than the near-field acoustic levitation. In the equal time, the restoring distance of objects moving with different accelerations after eccentricity increases significantly, which contributes to improve the speed and efficiency of non-contact transportation system. The study on the non-contact carrying and transportation technology proposed in this article will provide a novel method for the transportation of precision components such as optical lenses, silicon wafers, etc. [Display omitted] • A non-contact transportation method is proposed and its test prototype is fabricated. • The near-field acoustic levitation and negative pressure adsorption is used to realize levitation and restoring. • Experiments prove that the new method significantly improves the ability to transport objects. [ABSTRACT FROM AUTHOR]

• The study focuses on non-contact manipulation base on ultrasonic energy. • Ultrasonic transmitting units' working parameters are accurately determined and validated. • Levitating, restoring and rotation-driving mechanisms are investigated theoretically and experimentally. • Relation between levitation force and excitation voltage is revealed for precise control. • Stable levitation and rotation of disc-shaped objects is achieved without physical contact. To avoid the problems of wear, scratching, and contact pollution caused by traditional physical contact operations on high-precision materials or parts, a non-contact manipulation concept based on the near-field acoustic levitation effect and piezoelectric drive theory is proposed. The contact-free handling device can stably suspend the disc-shaped object and drive the object to rotate at a certain speed under the action of ultrasonic energy. The stable levitation capacity of the contact-free handling device relies on the vertical suspending force and horizontal restoring force derived from the W-type acoustic wave generated by the acoustic emission units. If the upper surface of the suspended disk has a specific configuration, a component driving force is generated when acoustic radiation is applied to it. To explore effective methods to improve the levitation effect, acoustic emission units were designed and fabricated, mathematical models of the suspending force and restoring force were built based on nonlinear acoustics and aerodynamics theories, and the influencing factors of these forces were investigated. In addition, a testing system for a contact-free manipulating device was fabricated to verify the levitation and driving performance using experimental methods. [Display omitted] [ABSTRACT FROM AUTHOR]