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Linear static response structural optimization has been developed fairly well by using the finite element method for linear static analysis. However, development is extremely slow for structural optimization where a non linear static analysis technique is required. Optimization methods using equivalent static loads (ESLs) have been proposed to solve various structural optimization disciplines. The disciplines include linear dynamic response optimization, structural optimization for multi-body dynamic systems, structural optimization for flexible multi-body dynamic systems, nonlinear static response optimization and nonlinear dynamic response optimization. The ESL is defined as the static load that generates the same displacement field by an analysis which is not linear static. An analysis that is not linear static is carried out to evaluate the displacement field. ESLs are evaluated from the displacement field, linear static response optimization is performed by using the ESLs, and the design is updated. This process proceeds in a cyclic manner. A variety of problems have been solved by the ESLs methods. In this paper, the methods are completely overviewed. Various case studies are demonstrated and future research of the methods is discussed.

Objective To investigate the hip joint forces, Von Mises stress, contact pressure and micro‐motion of hip prosthesis for developmental dysplasia of the hip (DDH) patients under different hip joint centers using musculoskeletal (MSK) multi‐body dynamics and finite element analysis. Methods Both MSK multi‐body dynamics model and finite element (FE) model were based on CT data of a young female DDH patient with total hip replacement and were developed to study the biomechanics of the S‐ROM hip prosthesis. The same offset of hip joint center along all six orientations compared with the standard position was set to predict its effects on both MSK multi‐body dynamics and contact mechanics during one gait cycle. Results The hip joint forces in the entire walking gait cycle showed two peak values and clear differences between them under different hip joint centers. The hip joint force increased when the hip joint center moved posteriorly (2101 N) and laterally (1969 N) to the anatomical center (1848 N) at the first peak by 13.7% and 6.6%, respectively. The hip joint force increased sharply when the hip center deviated laterally (2115 N) and anteriorly (2407 N), respectively, from the standard position (1742 N) at the second peak. For the sleeve of the S‐ROM prosthesis, the maximum Von Mises stress and contact pressure of the sleeve increased if the hip joint center deviated from the anatomical center posteriorly at the first peak. However, the Von Mises stresses and contact pressure increased at anterior and lateral orientations, compared to that of the standard position at the second peak. Small changes were observed for the maximum relative sliding distance along most of the orientations at both peaks except in the lateral and medial orientations, in which an increase of 8.6% and a decrease of 13.6% were observed, respectively. Conclusion The hip joint center obviously influenced the hip joint forces, stress, contact pressure and micro‐motion of the hip implant for this female patient. Comparison of the hip joint forces of under different center of rotation (COR) offsets for DDH hip implant: the predicted hip joint force varied with the walking gait on and showed two peaks for different COR of hip joint center; the maximum and minmum hip joint forces were obtained when the hip joint center moved to posterior and medial orientations (the maximum value: 2101 N, the minmum value: 1564 N) at first peak, respectively. The maximum and minmum values of hip joint force at the second peak were 2407 and 1304 N, respectively.

When a train crashes with another train at a high speed, it will lead to significant financial losses and societal costs. Carrying out a train-to-train crash test is of great significance to reproducing the collision response and assessing the safety performance of trains. To ensure the testability and safety of the train collision test, it is necessary to analyze and predict the dynamic behavior of the train in the whole test process before the test. This paper presents a study of the dynamic response of the train in each test stage during the train-to-train crash test under different conditions. In this study, a 1D/3D co-simulation dynamics model of the train under various load conditions of driving, collision and braking has been established based on the MotionView dynamic simulation software. The accuracy of the numerical model is verified by comparing with a five-vehicle formations train-to-train crash test data. Sensitivities of several key influencing parameters, such as the train formation, impact velocity and the vehicle mass, are reported in detail as well. The results show that the increase in the impact velocity has an increasing effect on the movement displacement of the vehicle in each process. However, increasing the vehicle mass and train formation has almost no effect on the running displacement of the braking process of the traction train. By sorting the variables in descending order of sensitivity, it can be obtained that impact speed > train formation > vehicle mass. The polynomial response surface method (PRSM) is used to construct the fitting relationship between the parameters and the responses.

In this study, the effects of in vivo (head flexion‐extension, lateral bending, and axial rotation) and in vitro (ISO 18192‐1) working conditions on the wear of ultrahigh molecular weight polyethylene (UHWMPE)‐based cervical disc prosthesis were studied via numerical simulation. A finite‐element‐based wear prediction framework was built by using a sliding distance and contact area dependent Archard wear law. Moreover, a pre‐developed cervical spine multi‐body dynamics model was incorporated to obtain the in vivo conditions. Contact mechanic analysis stated that in vitro conditions normally led to a higher contact stress and a longer sliding distance, with oval or crossing‐path‐typed sliding track. In contrast, in vivo conditions led to a curvilinear‐typed sliding track. In general, the predicted in vivo wear rate was one order of magnitude smaller than that of in vitro. According to the yearly occurrence of head movement, the estimated total in vivo wear rate was 0.595 mg/annual. While, the wear rate given by the ISO standard test condition was 3.32 mg/annual. There is a significant impact of loading and kinematic condition on the wear of UHMWPE prosthesis. The work conducted in the present study provided a feasible way for quantitatively assessing the wear of joint prosthesis.

The problem of friction reduction and wear resistance of sliding bearings is one of the key factors in determining the overall performance of internal combustion engines. This paper investigated and summarized the theoretical and simulation models of multi-body dynamics of crankshaft system, tribology of sliding bearings, and the wear calculation methods of the shaft-bearing friction pairs. Existing studies show that the dynamics model, hybrid lubrication model, and the friction and wear models request to be upgraded by comprehensively considering the material, structure, manufacturing process, working conditions, and etc. Based on the research status and existing problems of the above analyses, this paper summarizes the simulation models applicable to the field of dynamics and tribology of sliding bearings and presents the prospects for optimization of wear calculation methods for sliding bearings.

Near rectilinear halo orbits (NRHOs), a subset of the L1 and L2 halo orbit families, are strong candidates for a future inhabited facility in line with the goals for NASA’s long-term cislunar transportation network. Higher-period dynamical structures that bifurcate from the NRHO region of the L2 halo family offer additional insight into motion departing from or arriving into the vicinity. Characteristics of the NRHOs and the higher-period orbits, including stability and eclipse-avoidance properties, are presented and their persistence is verified in a higher-fidelity ephemeris model.

Rolling element bearing faults significantly contribute to overall machine failures, which demand different strategies for condition monitoring and failure detection. Recent advancements in machine learning even further expedite the quest to improve accuracy in fault detection for economic purposes by minimizing scheduled maintenance. Challenging tasks, such as the gathering of high quality data to explicitly train an algorithm, still persist and are limited in terms of the availability of historical data. In addition, failure data from measurements are typically valid only for the particular machinery components and their settings. In this study, 3D multi-body simulations of a roller bearing with different faults have been conducted to create a variety of synthetic training data for a deep learning convolutional neural network (CNN) and, hence, to address these challenges. The vibration data from the simulation are superimposed with noise collected from the measurement of a healthy bearing and are subsequently converted into a 2D image via wavelet transformation before being fed into the CNN for training. Measurements of damaged bearings are used to validate the algorithm’s performance.

Recent experiences have shown that one of the main causes of heavy vehicle crashes is the braking performance. In particular, when having to decelerate in an emergency situation, such as when an unexpected object is in the road. Thus, the capability of a vehicle to come to a safe stop is one of the most important factors in preventing more accidents. Safe braking distance is influenced by many factors, such as brake pedal force, the vehicle’s loading conditions, the travel speed and the road surface conditions. The aim of this study was to analyse the effect of the driver’s brake pedal force on braking distance during an emergency situation, allowed for a wide range of heavy vehicle’s GVW and speed. This study is carried out by using a multi-body dynamics simulation of a Single Unit Truck based on the validated vehicle model. Braking performance was estimated in terms of braking distance on a straight road with a wet surface. The findings from the braking distance simulation suggest a non-linear relationship between brake pedal force and braking distance. Finally, it reveals that, depending on the wheel lock-up situation, braking distance increases with increasing brake pedal force, and that the braking distance on a wet road is significantly affected by both the heavy vehicle’s GVW and speed.

The geological conditions in coal mine tunnel construction are complex, the vibration impact of shield machine due to rock breaking easily leads to cutters failure, thus causing safety problems and causing economic losses. In order to explore the fault vibration characteristics of shield cutters in rock breaking process, numerical simulation of rock breaking of single-blade fault cutters is carried out based on finite element-multi-body dynamics coupling model. The accuracy and reliability of simulation results are verified by comprehensive application of dynamic energy conservation law and hourglass energy control theory, and the fault vibration characteristics of cutter center, cutter body outer side and rock surface outer side are analyzed, and the influence of penetration degree and blade type on fault vibration characteristics is explored. The result showed that: in the three stages of initial contact-leaving rock-secondary contact, the axial and lateral linear velocity of cutter body decreases sharply, the normal linear velocity increases sharply, and the axial and lateral angular velocity of cutter increases sharply at the initial stage of contact. During the second contact period, the axial and lateral linear velocity of the cutter body increases sharply, the normal linear velocity decreases sharply, and the axial and lateral angular velocity of the cutter decreases sharply, and an obvious deviation trend is formed. And that, the fault characteristics of eccentric grinding cutter will appear earlier than fracture cutter, but it takes longer to fully manifest, and the vibration intensity of cutter decreases significantly with the increase of wear degree. In addition, angular velocity and angular acceleration data on rock surface are derived by displacement gradient tensor and numerical differentiation method, and it is found that fault vibration characteristics are not obvious on the outer side of rock surface. Meanwhile, through conducting indoor shield fault roller cutter rock-breaking experiments, the accuracy and rationality of the numerical simulation were verified. This paper provides a theoretical basis for the identification of fault cutter in multi-cutter system and complex shield construction conditions.

Aircraft landing gear assemblies comprise of various subsystems working in unison to enable functionalities such as taxiing, take-off and landing. As development cycles and prototyping iterations begin to shorten, it is important to develop and improve practical methodologies to meet certain design metrics. This paper presents an efficient methodology that applies high-fidelity multi-disciplinary design optimization techniques to commercial landing gear assemblies, for weight, cost, and structural performance by considering both structural and dynamic behaviours. First, a simplified landing gear assembly model was created to complement with an accurate slave link subassembly, generated based of drawings supplied from the industrial partner, Safran Landing Systems. Second, a Multi-Body Dynamic (MBD) analysis was performed using realistic input motion signals to replicate the dynamic behaviour of the physical system. The third stage involved performing topology optimization with results from the MBD analysis; this can be achieved through the utilization of the Equivalent Static Load Method (ESLM). Lastly, topology results were generated and design interpretation was performed to generate two designs of different approaches. The first design involved trying to closely match the topology results and resulted in a design with an overall weight savings of 67%, peak stress increase of 74%, and no apparent cost savings due to complex features. The second design focused on manufacturability and achieved overall weight saving of 36%, peak stress increase of 6%, and an estimated 60% in cost savings.