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Toe joint is known as one of the critical factors in designing a prosthetic foot due to its nonlinear stiffness characteristic. This stiffness characteristic provides a general feeling of springiness in the toe-off and it also affects the ankle kinetics. In this study, the toe part of the prosthetic foot was designed to improve walking performance. The toe joint was implemented as a single part suitable for 3D printing. The various shape factors such as curved shape, bending space, auxetic structure, and bending zone were applied to mimic human foot characteristics. The finite element analysis (FEA) was conducted to simulate terminal stance (from heel-off to toe-off) using the designed prosthetic foot. To find the structure with characteristics similar to the human foot, the optimization was performed based on the toe joint geometries. As a result, the optimized foot showed good agreement with human foot behavior in the toe torque-angle curve. Finally, the simulation conditions were validated by comparing with human walking data and it was confirmed that the designed prosthetic foot structure can implement the human foot function. [ABSTRACT FROM AUTHOR]

The seismic performance of slopes is typically evaluated with a pseudo-static method using equivalent horizontal load or with Newmark sliding block analysis. In both procedures, the definition of the potential sliding surface is a required input. The sliding surface has been reported to be marginally influenced by the input ground motion and, therefore, is most often assumed from a pseudo-static procedure. In this study, extensive series of two-dimensional dynamic nonlinear finite element analyses are performed to evaluate the sensitivity of the sliding surface on the slope geometry, soil strength parameters, and input ground motion characteristics. It is demonstrated that the sliding surface may vary with the intensity and frequency characteristics of the input motion. Slopes with inclination angle equal or less than 35° are shown to be marginally influenced by motion intensity if the mean period (Tm) < 0.3 s. However, slopes inclined at 45° are revealed to be more sensitive to the motion intensity and Tm. For motions with Tm > 0.3 s, the sliding surface is demonstrated to widen with an increase in the intensity of the input ground motions. The degree of widening increases proportionally with an increase in Tm. It is, therefore, recommended to derive sliding surfaces from a dynamic analysis for steep slopes. [ABSTRACT FROM AUTHOR]

Surgeons usually used short screws to avoid extensor tendon problems during volar locking plate fixation in distal radius fracture. However, the stability according to the length of distal locking screws have not been fully understood. We investigated this issue through finite element analysis and compression test using synthetic radius. Our results demonstrated that the bi-cortical full-length fixation does not contribute to the stiffness increase in the axial compression direction, and a reduction in length of up to more than 50% length can still provide similar stability to full-length screws. Our data can support that surgeon should undersize the distal screw. [ABSTRACT FROM AUTHOR]

A series of two-dimensional finite element analyses are performed to simulate the seismic response of slope composed of granular soil. Four sets of input parameters for the nonlinear soil model are used to fit the reference the shear modulus reduction and damping curves, thereby to evaluate the influence of the nonlinear soil model. The first set is fitted to the shear modulus reduction curve. The second and third sets are fitted simultaneously to both shear modulus reduction and damping curves. The final set applied the shear strength adjustment to adequately capture the nonlinear soil response at large strains. The accuracy of each set of parameters are evaluated through comparison with centrifuge model test measurements. It is observed that the nonlinear soil model has a marginal influence on the acceleration response. On the contrary, the vertical settlement is highly influenced by the nonlinear soil model. The discrepancy is shown to increase with an increase in the intensity of the input ground motion. It is demonstrated that the adjustment for the shear strength is important in performing seismic analyses of slopes, which is most often ignored in practice. Based on the results, practical guidelines on how to select the parameters for the nonlinear soil model are provided. [ABSTRACT FROM AUTHOR]

Computer-controlled optical surfacing provides superior optical fabrication performance with low-cost mass production over conventional method relying heavily on the skills of optician. However, there are still lots of technical issues to be resolved in computer-controlled optical surfacing, and edge effect has been regarded as one of the most challenging tasks for years due to the unpredictable behaviors of a polishing tool. As a polishing tool approaches the edge of the workpiece, the tool-workpiece contact area decreases and this in turn accompanies the tool-workpiece misfit and non-uniform pressure distribution. Thus, the edge effects should be taken into account in deterministic polishing technique. In this paper, we suggest new edge tool influence functions by modeling the velocity and pressure distribution of a polishing tool with eccentric rotation motion. Here, the finite element analysis was used to accurately predict the non-linear behaviors of a polishing tool at the edge. We verified our proposed method by comparisons with experimental results, and it shows considerable resemblance between them. [ABSTRACT FROM AUTHOR]

Hybrid or aluminum tube structure requires reliable joining of the shaft to other components such as steel yoke and universal joint, which is often the most difficult task. Therefore, a reliable joining method between the aluminum tube and the steel yoke of a hybrid composite propeller shaft for automobile is required. In this work a press fitting method for joining of an aluminum tube to an aluminum yoke is devised by a steel ring with many small teeth to increase reliability as well as to reduce manufacturing cost of the hybrid propeller shaft rather than using other joining methods such as adhesively bonded or welded joints. The optimal shape and number of teeth of the steel ring were obtained experimentally for the maximum static torque capabilities and fatigue characteristics of the press fit joint, and was compared to the finite element analysis results. Finally, a design guideline for the press fit joint using a steel ring with many small teeth for joining the aluminum shaft to the steel ring was suggested. With the developed press fit joint, the static average shear strength of 70 MPa and fatigue strength of 21 MPa between the aluminum tube and the steel ring were realized, which were almost three times higher than that of the adhesively bonded joint. [ABSTRACT FROM AUTHOR]

Abstract: The present work studies the moisture induced failures of a stacked-die package. The study includes various experimental tests to find the characteristics of constituent packaging materials such as interfacial strength, hygro-swelling property and vapor pressure, and a comprehensive finite element analysis integrating the effects of the hygro-swelling stress, the thermo-mechanical stress and the vapor pressure. Specifically, the vapor pressures with respect to the moisture concentration and the temperature in epoxy molding compound were characterized experimentally by combined TMA/TGA technique. In the numerical stress analysis, the interfacial delamination was newly simulated by applying a cohesive element modeling technique, in which a quadratic traction damage initiation law and an exponential displacement separation law were used. [Copyright &y& Elsevier]

Abstract: The micro-multi-functional actuator (MFA) of a cellular phone is a mass-spring system which is resonated by electrical force at the fundamental natural frequency to generate and transmit the vibration signal to the customers. The MFA has two design requirements such as high vibration force transmission and long fatigue life. Generally, conventional multi-functional actuators have been manufactured using stamped metal plate springs using precision dies. Since cracks are often generated in the cut area of metal plate during stamping operation, fatigue failures of conventional MFA’s are inevitable. In this study, a new micro-multi-functional actuator was designed using a spring (music) wire which has a high fatigue endurance limit because the surface of music wire is finely surface-finished. After the static and dynamic characteristics of MFA were analyzed using finite element analysis with respect to the diameter and shape of the spring wire, its dynamic performance such as fundamental natural frequency, vibration force transmission and fatigue life, and adhesion characteristics between the wire and the composite molding were experimentally investigated with respect to manufacturing parameters such as surface treatment method of spring wire, injection molding temperature and pressure of polymer mold. [Copyright &y& Elsevier]

Abstract: Substituting composite structures for conventional metallic structures has many advantages because composite materials have both high specific stiffness and damping characteristics compared to conventional metallic materials. In this study, circular plate cutting tools which are used for rough machining of bearing sites in crankshafts or camshafts were designed with the fiber reinforced composite material to reduce tool mass and to improve the dynamic stiffness of circular plate cutting tools. The hybrid steel/composite circular plate cutting tool was analyzed by finite element method with respect to material types such as composite and foam, stacking angles of the composite, adhesive bonding thickness, and dimensions of the cutting tool. Also, the constrained damping characteristics of the tools were experimentally investigated with respect to the adhesive bonding thickness and material type such as composite and PVC foam. From the finite element analysis and experimental results, optimal design parameters for the hybrid steel/composite circular plate cutting tool were suggested. [Copyright &y& Elsevier]

In this work, damage sensing of carbon fiber reinforced polymer composite (CFRP) was conducted based on an addressable conducting network (ACN). To improve the accuracy of damage detection, a deep learning-based damage sensing system was developed. The data for deep learning were generated using a resist network model based on Kirchhoff's law. The generated data was verified through finite element analysis. Then, the Artificial Neural Network (ANN) deep learning algorithm was used for damage detection and evaluation. The accuracy of damage sensing was improved by applying the resist network model that considered not only delamination but also the damage of the carbon fiber. As a result, damage detection of CFRP was performed with a high accuracy rate of about 95%. [ABSTRACT FROM AUTHOR]

Abstract In this study, the strain rate dependent mechanical behavior of glass fiber reinforced thermoplastic polypropylene (GFPP) was investigated under the high strain rate. The split Hopkinson pressure bar (SHPB) apparatus was used in order to investigate the effects of strain rate based on the dynamic tensile, compressive and bias-extension shear behavior. The failure mode in fracture surface of each specimen was analyzed by using the scanning electron microscopy with respect to the strain rate. Additionally, the impact simulation of bumper beam was conducted to verify the measured strain rate dependent mechanical behavior of GFRP by using the commercial finite element analysis software LS-Dyna. Finally, it was found that the impact response of GFRP structures could be accurately predicted by using the strain rate dependent mechanical behavior compared to those of quasi-static properties. [ABSTRACT FROM AUTHOR]

In this work, a novel deep neural network was proposed for predicting the mechanical behavior of plain carbon fabric reinforced woven composites. The deep neural network was trained by a pre-simulated stress-strain curve database of woven composites depending on yarn structures and the mechanical properties of the fiber and matrix. Micro-mechanics-based multi-scale analyses of woven composites were conducted for progressive damage analysis. These analyses utilized the stress amplification factor to transfer stress between the micro-scale and meso-scale simulations and the respective failure criteria were applied for micro-scale stresses of the fiber and matrix, respectively. The database of stress-strain curves under tensile, compressive and shear loading was acquired for different yarn geometries and constituent properties. These variables were used as training input and the resulting stress-strain curves were used as training output of the network. To optimize the network, hyper parameters of the neural network, such as the number of layers and nodes, were determined by the Hyperband optimization algorithm. The train and test of deep neural network model was performed by TensorFlow backend using the Keras library in Python. Mechanical tests were performed to validate the predicted mechanical behavior from both simulation and the deep neural network. As a result, the stress-strain curves under tensile, compressive and shear loading of arbitrary woven carbon composites can be successfully predicted in several seconds by the deep neural network with high accuracy. [ABSTRACT FROM AUTHOR]

In this study, a low-velocity impact test of glass fiber-reinforced polypropylene (GFPP) composites was simulated considering interlaminar fracture toughness. In the simulation, intralaminar and interlaminar damage were modeled using the continuum damage mechanics (CDM) and cohesive zone method (CZM) models, respectively. The B-K criterion was used for the interlaminar damage model along with experimental results, which were obtained from fracture toughness tests of modes I and II and the mixed mode. Low-velocity impact tests were performed to verify the developed damage model, and various characteristics such as delamination and the force–displacement were evaluated. Finally, it was found that the developed damage model with interlaminar fracture toughness can be used to accurately predict the impact behavior of GF/PP composites, including interlaminar delamination. [ABSTRACT FROM AUTHOR]

Recently, the electric mobility has emerged with great prospects as there has been a growing interest in and demand for eco-friendly energy. The electric vehicle uses a large number of lithium batteries as sources of power, and the lithium battery poses a risk of fire and explosion when the external impact is loaded. Therefore, in this study, an underbody shield (UBS) was designed and manufactured using carbon fiber reinforced thermoplastic composites for battery protection. The underbody shield is composed of two parts, which are the main shield plate and collision protection bar (CPB). Mechanical behavior against impact was analyzed through finite element analysis considering the position of the CPB and the shape of the underbody shield plate. For the UBS, the hybrid composites (Carbon fiber (CF)/polyethylene terephthalate (PET) and self-reinforced polypropylene (SRPP) composites) were used and the ratio between the CF/PET and SRPP was optimized. Through a finite element analysis, the optimal underbody shield was designed with a thickness of 2.4 mm and a hybrid ratio of CF/PET:SRPP as 1:2. Finally, the designed underbody shield was manufactured using a thermo-forming process and mounted to an electric vehicle, and then a vehicle crash test was performed with a concrete obstacle. The developed underbody shield could protect the battery against the impact damage successfully, showing that the deformation of a rear part was within 5 mm and no battery leakage occurred. [ABSTRACT FROM AUTHOR]

Abstract: Carbon–phenolic woven composite materials are employed in heavy duty bearings due to their inherent self-lubricating properties and thermal stability. In this work, a hybrid composite hemispherical bearing (CHB) composed of carbon–phenolic composite and aluminum back-up for the suspension of high mobility tracked vehicles, is developed. In order to reduce the damage generated during machining of the spherical surface of CHB, a near net-shape molding process was used. The thermal residual stresses in the composite and aluminum generated during molding process were calculated by finite element analysis with respect to the fiber types and material stacking sequences. From the calculated data and tested results for CHB, it was found that the developed CHB performed better than the conventional carbon-PEEK CHB. [Copyright &y& Elsevier]

Polymers are highly affected by moisture and temperature in terms of reliability of packaging. Especially, interface delamination between dissimilar materials with polymer is one of the major issues to the structural integrity and reliability, which is affected significantly by temperature and moisture concentration. In this paper, moisture absorption characteristics and thermo-mechanical delamination of semiconductor packages were predicted by finite element analysis considering moisture and temperature changes during the reflow process simultaneously based on a home-made user's subroutine. To implement the delamination through finite element analysis, moisture absorption experiments were conducted to evaluate hygroscopic properties (diffusivity, concentration) of the package material with different relative humidities (RH) and temperatures. In addition, adhesion strength of bi-material was evaluated by a micro-scale shear test. The measured adhesion strength of bi-material such as Epoxy molding compound (EMC)/Chip, Chip/substrate, and substrate/EMC were implemented in the user's subroutine with respect to the moisture concentration and temperature. The user's subroutine based finite element analysis code was developed to analyze the combined effect of hygroscopic and thermal deformation. As a result, interface delamination was successfully predicted considering the in-situ moisture desorption and temperature increase during the reflow process and interfacial failure strength considering the temperature and moisture concentration. • Prediction of moisture absorption characteristics and thermo-mechanical delamination of semiconductor packages • Evaluation of hygroscopic properties of package material with different relative humidity and temperatures • Adhesion strength measurement of bi-material with respect to the moisture concentration and temperature [ABSTRACT FROM AUTHOR]