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A shear connection used in composite structures consisting of perforated steel strips has been under investigation for almost forty years. During this time, several suitable shapes of perforated strips were investigated. Many of them provide sufficient behaviour in the transmission of longitudinal shear between a steel beam and a concrete slab. Instead of developing a completely new shape of the recesses in the perforated strip with unknown behaviour under static and dynamic loading, a steel strip already examined was chosen as the reference type for this study. Subsequently, a topology optimization procedure was performed to analyse the possibilities of shape customization to improve behaviour by increasing not only the resistance of the entire shear connection but also the ductility of the steel strips. Based on the results of the verifications, this procedure showed possibilities for improvement but also deterioration of the properties of the examined perforated steel strips, as well as other types of strips. Furthermore, by appropriate rearrangement of the reinforcement bars, the increase in resistance value can be significantly higher. [ABSTRACT FROM AUTHOR]

Guided acoustic waves are commonly used in domestic water meters to measure the flow rate. The accuracy of this measurement method is affected by factors such as variations in temperature and limescale deposition inside of the pipe. In this work, a new approach using signals from different sound propagation paths is used to determine these quantities and allow for subsequent compensation. This method evaluates the different propagation times of guided Lamb waves in flow measurement applications. A finite element method-based model is used to identify the calibration curves for the device under test. The simulated dependencies on temperature and layer thickness are validated by experimental data. Finally, a test on simulated data with varying temperatures and limescale depositions proves that this method can be used to separate both effects. Based on these values, a flow measurement correction scheme can be derived that provides an improved resolution of guided acoustic wave-based flow meters. [ABSTRACT FROM AUTHOR]

Wafer warpage occurs during the fabrication process, which induces many issues such as wafer handling, lithography alignment, device reliability. The efficiency of dicing street on wafer warpage reduction is investigated by varying the width, depth, and pitch of dicing. With the finite element method simulation results, decreasing the dicing pitch to a quarter-pitch shows a 43.7% warpage reduction. We reveal that the method of decreasing the dicing pitch is more efficient on wafer warpage reduction than that of increasing the dicing width or depth. Furthermore, the efficiency of warpage reduction by decreasing the dicing pitch is confirmed by experiments, which shows a good agreement with the simulated results. The method of decreasing the dicing pitch cut each part smaller. These small parts deform locally instead of continually over the whole wafer, resulting in an efficient wafer warpage reduction. This research provides guidelines for chiplet design or optimization of chip size to reduce the wafer warpage. [ABSTRACT FROM AUTHOR]

The goal of this study was to explore the self-guided machining mechanism of boring and trepanning association (BTA) deep hole drilling and realize precise control of the machining quality. The motion analysis method was used to analyze the center motion trajectory of the drill during the entrance, and the self-guiding mechanism and hole-forming mechanism of BTA deep hole drilling were revealed. Considering the bending deformation of the drilling tube and the tool structure parameters, according to the elastic-plastic deformation theory and Hertzian contact theory, a novel analytical model of the extrusion contact between the guide pads and the hole wall of the BTA deep hole drilling was established for the theoretical prediction of the extrusion deformation and the machining hole diameter. Combined with the finite element method (FEM) simulation model, the variation law of the contact inclination angle, contact stress, and extrusion deformation of the guide pads and the hole wall with the drilling conditions were studied. The total extrusion deformation between the guide pad and the hole wall was between 10 and 50 μm. The maximum error between the FEM simulation results and the test results was 18.1%, and the maximum error between the analytical model results and the test results was 23.6%. The simulation and experimental results showed that the established extrusion contact model could accurately predict the extrusion deformation of the hole wall and the machining hole diameter. [ABSTRACT FROM AUTHOR]

The folded sandwich structure might inevitably be impacted at low velocity when it is working, which will lead to the decline of the mechanical properties. The low-velocity impact resistance of the double-layer V-shaped aluminium folded sandwich structure is researched by the finite element method. It was found that the damage mode and the proportion of energy absorption of the double-layer and single-layer folded sandwich structures are different under low-velocity impact, and the impact stiffness and energy-absorbing capacity of the double-layer structure are better than those of the single-layer structure when the impact energy is small. In addition, in view of the low-velocity impact response characteristics of the double-layer V-shaped aluminum folded sandwich structure, two methods are proposed to improve its impact stiffness. Both methods ensure that the total mass of the structure remains unchanged. One method keeps the inner panel still and changes the wall thickness distribution of the top and bottom cores, and the wall thickness of the top core is increased. The other method keeps the wall thickness of the cores unchanged, and the inner panel is moved upward. From the finite element results, it can be seen that after increasing the wall thickness of the top core from 0.25 mm to 0.4 mm, the maximum impact distance of the impactor decreases by 30.3% when the impact energy is 5 J, and it decreases by 23.1% when the impact energy is 10 J, and with 20 J, it decreases by 14.5%. After reducing the height of the top core from 12.5 mm to 5 mm, the maximum impact distance of the impactor is reduced by 22.86% when the impact energy is 5 J, 21.85% when the impact energy is 10 J, and 20.51% when the impact energy is 40 J. The improvement is obvious. The two methods can increase the equivalent density of the top core, which can increase the stiffness of the top core. For the double-layer structure, the stiffness of the top core near the impact point has a greater influence on the low-velocity impact resistance of the entire structure. [ABSTRACT FROM AUTHOR]

To obtain excellent mechanical properties from large cross-sections of plastic mould steel (SDP1), we conducted multi-directional forging (MDF) to control the microstructure of ingots. To investigate the microstructural evolution of SDP1 steel during MDF, we performed hot forging at 1150 °C using a THP01–500A hydraulic press. The dimensions of the specimens were Φ38 mm × 80 mm. The microstructure of the specimens after forging was observed under a metallographic microscope. Furthermore, the results of the finite element method (FEM) simulations were employed to improve the quality of the forgings. The predicted results agreed well with the experimental ones, indicating that FEM is effective for analysing microstructural evolution during MDF. Thus, MDF for large cross-sections of SDP1 steel (Φ1000 mm × 2200 mm) was simulated. The results showed that the average grain size of SDP1 steel at the core of an ingot after MDF ranged from 40.6 to 43.3 μm. Although this was slightly higher than the grain size of the sample after traditional upsetting and stretching forging (TUSF) (35.7–46.0 μm), the microstructure of the SDP1 steel sample after MDF was more uniform than that after TUSF. Compared with TUSF, MDF not only refines the grain size but also improves the microstructure uniformity of the sample. [ABSTRACT FROM AUTHOR]

The article presents precision and numerically stable method of calculation of the characteristic impedance of cylindrical multilayer waveguides used in high-precision wideband measuring instruments and standards, especially calculable thermal converters of AC voltage and precision wideband current shunts. Most of currently existing algorithms of characteristic impedance calculation of such waveguides are based upon approximations. Unfortunately, application of such methods is limited to waveguides composed of a specific, usually low number of layers. The accuracy of approximation methods as well as the number of layers is sometimes not sufficient, especially when the coaxial waveguide is a part of precision measurement equipment. The article presents the numerically stable matrix analytical formula using exponentially scaled modified Bessel functions to compute characteristic impedance and its components of the cylindrical coaxial multilayer waveguides. Results obtained with the developed method were compared with results of simulations made using the Finite Element Method (FEM) software simulations. Very good agreement between results of those two methods were achieved. [ABSTRACT FROM AUTHOR]

In this study, the evolution of mechanical properties, microstructure, and residual stresses during selective laser melting of CuSn10 components was studied. To provide a proper material model for the simulations, various CuSn10 parts were manufactured using selective laser melting and examined. The manufactured parts were also used to validate the developed model. Subsequently, a sequentially coupled thermal–mechanical FEM model was developed using the Ansys software package. The developed model was able to deliver the mechanical properties, residual stresses, and microstructure of the additively manufactured components. Due to introducing some simplifications to the model, a calibration factor was applied to adjust the simulation results. However, the developed model was validated and showed a good agreement with the experimental results, such as measured residual stresses using the hole drilling method, as well as mechanical properties of manufactured parts. Moreover, the developed material model was used to simulate the microstructure of manufactured CuSn10. A fine-grain microstructure with an average diameter of 19 ± 11 μm and preferred orientation in the Z-direction, which was the assembly direction, was obtained. [ABSTRACT FROM AUTHOR]

• Finite element simulation of miniaturized housing structure for 3D packaged MEMS thermal wind sensor model. • Experiments are also done firstly, an agreement between simulation and experiment is obtained. • Provide a reference for the design and manufacture of MEMS thermal wind sensor miniaturization package. [Display omitted] This paper, for the first time, investigates the effects of miniaturized housing structure with various parameters on micro-electro-mechanical systems (MEMS) thermal wind sensors by simulation and experiments. Pillar diameter, number, height and curve-shaped top cover with different radian are considered to find out their influence on sensors performance. In the simulation, finite element method (FEM) software COMSOL is applied to simulate the 3D packaged sensor model. Then sensors with different housing parameters are tested in the wind tunnel based on thermal calorimetric principle, which uses flow-induced temperature gradient between symmetrically distributed thermistors to represent wind speed. An agreement between simulation and experiment is obtained, and the results demonstrate that the device's performance can be improved with smaller pillar diameter, more pillar number, and smaller pillar height. Moreover, the curved roof is designed, which provides a possibility for high wind speed measurement. [ABSTRACT FROM AUTHOR]

Azobenzene‐functionalized liquid crystalline polymer networks (azo‐LCNs) are promising candidates for light‐fueled contactless manipulation of miniaturized soft robots through embedding photoactive molecular switches into alignment‐programmable LCNs. In particular, the 3D helical geometry of azo‐LCNs is reported to achieve rapid photomotility by introducing rolling resistance. However, the maximum height of the obstacle that soft robot can overcome is limited by the helix diameter and the stress–strain responsivity. Herein, the helical diameter per unit length and photogenerated stress through molecular engineering of photoactive molecular switches are maximized. The carbon number of aliphatic spacers in the photoactive molecular switches is varied from two to eight to systematically investigate the structure–property–performance relations by studying the molecular geometry, physical properties of polymers, and photomotility of polymers. Furthermore, a finite‐element analysis simulation is presented to understand the rolling locomotion of helical torsional soft robots. Through molecular engineering, the helix diameter per unit length of 0.2 mg soft robots is maximized, demonstrating high Young's modulus (≈2 GPa) and photogenerated stress (>1 MPa), as well as large velocity per body length, compared with the previously reported soft robots. Finally, the molecularly engineered soft robots successfully climb stairs, which is a key task in robotic systems. [ABSTRACT FROM AUTHOR]

Back-to-back geosynthetic-reinforced soil walls (BBGRSWs) are commonly used in embankments approaching bridges and narrow spaces. However, the available literature and design guidelines for BBGRSWs are limited. The aims of this research were to develop a greater understanding of the working performance of BBGRSWs and to optimize the design method of a BBGRSW to ensure the cost-efficiency as well as the stability of the structure. On the basis of a monitored BBGRSW structure located in China, we established a numerical model. The parameters of the materials used in the actual project were determined through triaxial and tensile tests. The numerical results were compared with the measured results in the field to verify the correctness of the selected parameters. Two parameters were investigated by the FEM method: the reinforcement length and the arrangement. The FEM analysis indicated that post-construction deformations such as displacement and settlement could be reduced by reinforcing the same layer on both sides. Longer reinforcements were needed to achieve the same performance if the reinforcements were cross-arranged. Thus, BBGRSWs can have a superior performance if the reinforcements are connected in the middle from both sides. Even with longer reinforcements, the safety factor of the wall with a cross-arranged reinforcement was smaller than that with same-layered reinforcements. [ABSTRACT FROM AUTHOR]

• A comprehensive simulation conducted to explore laser-ultrasonic waves in CFRP. • Derivations of temperature and thermal force fields due to laser absorption. • Investigations on the effect of oblique laser incidence. • Revealing the directivity of Lamb wave amplitude. • Experimental verification to guarantee the accuracy of the simulation results. Laser-ultrasonic waves are used in nondestructive inspections because they can be excited on arbitrarily shaped surfaces by irradiation of a pulsed laser from a distance. During the non-contact scanning of a laser, the waveform of excited ultrasonic wave is changed because the incident angle varies substantially. The change of the waveform will be more obvious for carbon fiber reinforced plastics (CFRP) laminates that have anisotropic properties. In order to guarantee the inspection, in this paper, we investigated the generation of ultrasonic waves in CFRP laminates by a laser irradiation with various incident angles and azimuth angles. Firstly, we constructed a simulation model: the thermal force field caused by the laser absorption is derived from a heat conduction equation, and it is introduced into an FEM software for analyzing the propagation behavior of generated ultrasonic waves. Then, the simulation result is compared with an experiment result. Through the FEM analysis, we found that the amplitude of the excited waves has an obvious directivity because of the strong anisotropy in the thermo-elastic property of the CFRP. In addition, the change in propagation behavior in the case of a small incident angle of 30° was found to be inconspicuous. However, when the incident angle of the laser beam is larger than 60°, the directivity pattern changes depending on the azimuth angle. Thus, it is important to control the incident angle and direction when a laser ultrasonic inspection is applied to CFRP structures. [ABSTRACT FROM AUTHOR]

Handling plastic waste through recycling allows extending the life of polymeric materials, avoiding recurrence to incineration or landfilling. In contrast with traditional mechanical recycling technologies, chemical recycling enables the obtention of the virgin monomers by means of depolymerisation to create new polymers with the same mechanical and thermal properties as the originals. Research presented in this paper is part of the polynSPIRE project (Horizon 2020 European funding programme) and develops and scales-up a heated reactor to carry out the depolymerisation of polyamide-6 (PA6), polyamide-6,6 (PA66) and polyurethane (PU) using microwave (MW) technology as the heating source. The purpose is to design and optimize a MW reactor using up to eight ports emitting electromagnetic waves. Finite element method (FEM) simulation and optimisation are used to design the reactor, considering as parameters the data obtained from experimental dielectric testing and lab-scale characterisation of the processes and materials studied. Two different COMSOL Multiphysics modules are involved in this work: Radio Frequency (RF) and Chemical Reaction Engineering (RE), to simulate the reactor cavity using two frequency levels (915 MHz and 2.45 GHz) with a power level of 46 kW, and the chemical depolymerisation process, respectively. A sensitivity study has been performed on key parameters such as the frequency, the number of ports, and position inside the reactor to consolidate the final design. It is expected that these results assist in the design and scale-up of microwave technology for the chemical recycling of plastics, and for the large-scale deployment of this sustainable recovery alternative.

Laser-ultrasonic waves are used in nondestructive inspections because they can be excited on arbitrarily shaped surfaces by irradiation of a pulsed laser from a distance. During the non-contact scanning of a laser, the waveform of excited ultrasonic wave is changed because the incident angle varies substantially. The change of the waveform will be more obvious for carbon fiber reinforced plastics (CFRP) laminates that have anisotropic properties. In order to guarantee the inspection, in this paper, we investigated the generation of ultrasonic waves in CFRP laminates by a laser irradiation with various incident angles and azimuth angles. Firstly, we constructed a simulation model: the thermal force field caused by the laser absorption is derived from a heat conduction equation, and it is introduced into an FEM software for analyzing the propagation behavior of generated ultrasonic waves. Then, the simulation result is compared with an experiment result. Through the FEM analysis, we found that the amplitude of the excited waves has an obvious directivity because of the strong anisotropy in the thermo-elastic property of the CFRP. In addition, the change in propagation behavior in the case of a small incident angle of 30° was found to be inconspicuous. However, when the incident angle of the laser beam is larger than 60°, the directivity pattern changes depending on the azimuth angle. Thus, it is important to control the incident angle and direction when a laser ultrasonic inspection is applied to CFRP structures.

[Display omitted] • Analysis of non-uniformly distributed loads' effects on SAW sensor's response. • A novel 2-D segmentation method to calculate SAW sensor's response under multiple patterns of load's distribution. • FEM simulation of R-SAW modes with and without SiO 2 load. • Fabrication of a series of two-port R-SAW resonators with different load patterns. To accurately calculate the response of surface acoustic wave sensors with non-uniformly distributed loads, a two-dimensional segmentation method suitable for various load distribution patterns was established with the idea of channelization. In this method, the sensitive area of the sensor was divided into several channels in the direction of the aperture, and each channel was cut apart into several cells along the direction of acoustic wave propagation. Finally, the two-dimensional analysis of the non-uniform distributed load was completed since each cell was analyzed and cascaded. A Rayleigh surface acoustic wave (R-SAW) sensor was used to simulate and experiment in this paper. The results showed that the responses of SAW sensors under loads with the non-uniform distributions were simulated accurately by using a two-dimensional segmentation method. [ABSTRACT FROM AUTHOR]

The trend of electrification and miniaturization brings the reliability of interconnects to the forefront. The solder joints are subjected to thermo-mechanical mismatch due to the Joule heating and electromigration (EM)-induced degradation under high current stressing conditions. However, most of the studies are limited to lab test samples or lab test conditions, which lack transferability in engineering applications. In this paper, automotive electronic components are studied subjected to field-like current pulse conditions. The work aims to understand the field-relevant failure modes of solder joints exposed to high current stressing via experimental and numerical investigations. Shunt components with and without Ni plating are analyzed in power cycling tests. A polarity effect is observed in the growth of intermetallic compounds (IMCs). The thickness of IMC at the anode exhibits an approximately linear growth with current stressing time, whereas the thickness of IMC at the cathode remains almost unchanged or slightly decreased. Ni, as diffusion barrier, serves to restrain Cu consumption from the terminals of shunts and also reduces Cu mass transport into and within the solder. The net Cu flux at the interface and in the solder is discussed to analyze the IMC growth kinetics. The shunts with Ni plating undergo less EM of Cu and yield longer lifetime. Voids and crack formation are detected in computer tomography (CT) scans and cross-sectional analysis by scanning electron microscopy (SEM). Finite element method (FEM) is implemented to simulate thermo-electro-mechanical fields of the assembly under power cycling test conditions. The distribution of divergence of material flux density corresponds well with the location of voids formation and provides good estimation for the lifetime. • Field-relevant failure mode of solder joints under high current loads is reproduced and investigated. • A polarity effect is observed in the growth of intermetallic compounds and shunts with Ni plating yield a longer lifetime. • Simulation is performed to characterize electromigration and thermo-mechanical fatigue of the solder joint. • Lifetime of the solder is proportional to the inverse value of divergence of material flux density. • With longer stressing time, the strain in solder joint will be increased owing to voids formation and coalescence of voids. [ABSTRACT FROM AUTHOR]

The characterization and modeling of Ceiba plywood delamination requires extensive experimental and numerical study. A data reduction scheme, based on the compliance method and the concept of equivalent crack, is utilized. This method has two main advantages over conventional methodologies: it does not require crack monitoring during propagation and takes into account the effect of the fracture process zone at the crack tip. The characterization of delamination and the mechanical behavior of adhesive joint are influenced not only by the adhesive properties but also by the characteristics of the interface. Various modeling methods have been proposed to characterize the delamination of laminated materials. Among the most widely used methods is the cohesive zone model, which is based on fracture mechanics and damage theory and allows for an adequate prediction of the onset and propagation of the delamination simultaneously. This method consists of introducing a cohesion law in finite element modeling. Often, the determination of these parameters is obtained iteratively by matching the numerical results with the experimental results. In this study, the cohesive parameters of the bilinear traction–separation laws in each pure mode were determined. This identification was achieved through the design of experiments method and the Kriging metamodel. A finite element modeling of the Ceiba plywood delamination was then performed. The experimental tests carried out make it possible to assess the delamination resistance under mode I, mode II and mixed mode I + II loading. Following the description of the experimental procedure, the experimental and numerical results are presented and compared. Finally, the response to the delamination was represented by a semi-empirical criterion and an analysis of fracture surfaces was performed and interpreted. [ABSTRACT FROM AUTHOR]

In this study, the optimum position and minimum diameter of damping wire were investigated to maximize the fundamental frequencies of a rotating blade. The blade was modeled as an isotropic, homogenous and constant cross-sectional cantilever rotating beam. The damping wire was modeled as an intermediate elastic support. In most rotating-beam applications, such as turbine blades, the slenderness ratio is low; therefore, Timoshenko beam theory was selected to analyze the model. The optimal position and minimum stiffness of elastic support were determined to maximize the natural frequencies of the beam using the finite element method. Minimum diameter of the damping wire was calculated by determining the minimum stiffness. Parameter sensitivity analysis showed that the angular velocity of the blade has no remarkable effect on the optimal position and minimum diameter of damping wire. [ABSTRACT FROM AUTHOR]

This study aimed to assess particle swarm optimization (PSO) optimized with an adaptive network-based fuzzy inference system (ANFIS) for the prediction of the ultimate bearing capacity of strip footing resting on a sloping crest. To make datasets, a 2524 finite element model (FEM) simulation analysis was performed. In this sense, the k-fold validation technique selected for the selection of the testing and validation purposes. Also, the variables of the ANFIS algorithm (i.e., the number of clusters), and the PSO algorithm (the population size were optimized using a series of trial and error process. The second main objective of the current study was to assess the applicability of PSO–ANFIS in estimating the ultimate bearing capacity of the strip footing resting on a single cohesionless slope when it was subjected to an external vertical applied stress. The input parameters were the soil properties (Stype) (classified into five different classes from the weakest, shown as S1, to the strongest type, displayed in higher order), slope angle (β), setback distance ratio (b/B) (the distance of the footing from the slope crest to the footing width), and vertical settlement (Uy) of the footing, while the main output was the applied vertical stresses (Fy) that can be applied on the footing. Note that the ultimate bearing capacity (Fult) is the maximum vertical stress when Uy = 0.1 B. A thorough comparison between the measured FEM simulations, the proposed ANFIS and PSO–ANFIS models were carried out to demonstrate their effectiveness in predicting a reliable Fult resting on cohesionless slopes. [ABSTRACT FROM AUTHOR]

Grain loss in the harvesting process of combine harvesters not only causes economic losses to farmers but also affects the soil environment because of the lost grain covering the soil, influencing crop growth in the next season. Grain sieve loss-monitoring sensors represent an important accessory in combine harvesters, as they can not only provide current grain loss levels for the operator to adopt a rational action in time but also serve as an important performance signal for the control system. To reflect the rice grain sieve loss level of combine harvesters in real time, an indirect grain sieve loss-monitoring system is proposed in this paper. First, the grain collision rise time was obtained by the finite element method (FEM), and the parameters of the grain loss sensor signal processing circuit were determined accordingly to upgrade the monitoring accuracy. Then, grain loss distribution behind the cleaning shoe was analyzed in detail under different working parameters. Grain loss distribution functions at the end of the sieve and a monitoring mathematical model with relevant variables were established based on the laboratory experiment results. Finally, calibration experiments were carried out to verify the measurement accuracy of the sensor on a cleaning test bench, with an obtained relative monitoring error ≤6.41 % under different working conditions.

• Fibrous network materials are found to be insensitive to the crack when the crack length is less than a critical length. • The critical length of crack is three times as much as the average length of fiber segments. • Fiber re-orientation contributes to the enhancement of the crack resistance of the fibrous network materials. A 3D numerical model is established to characterize the fibrous network materials and the fracture behavior is investigated through the finite element method (FEM) analysis. The numerical results show that fibrous network material is insensitive to the crack when the crack length is less than a critical value, which is three times as much as the average length of fiber segments in the fibrous network. In addition, the toughening mechanism of the fibrous network material is revealed based on the FEM simulations. Due to the damage accumulation of bonds near the crack tip, the fibers around the crack tip are reoriented and become perpendicular to the crack path, which can further inhibit the crack propagation, and the deformation mode changes from bending-dominated deformation to tensile-dominated deformation, with the loading capacity of the fibrous network materials enhanced. The results in this paper demonstrate that the fibrous network materials show damage-tolerance to the small crack under the critical crack length, and the fibrous network formed by brittle fibers can exhibit ductile behaviors by controlling the microstructure and relative density, which is useful for the design and optimization of fibrous network materials. Image, graphical abstract [ABSTRACT FROM AUTHOR]

This paper aims to model and simulate tool wear in drilling of Inconel 718 under two different cooling conditions, using an innovative numerical procedure. Although tool wear models can be implemented in most of finite element analysis (FEA) software to calculate the tool wear rate, there is a great limit due to the inability of all these software to update the geometry of the worn tool. In order to overcome this limitation, a subroutine able to modify the tool geometry based on a given tool wear model was developed and implemented in DEFORM 3D, an implicit FEA software. Experimental tests were performed to measure tool wear in drilling using conventional metal working fluids (MWF) and liquid nitrogen (LN 2) cooling. Experimental data were used to calibrate the tool wear model and to validate the drilling models. A comparison between simulated and measured results demonstrated the suitability of the developed drilling model to predict tool wear under both MWF and LN 2 cooling conditions. Therefore, the developed model can be efficiently used to evaluate the influence of the cutting conditions (including cooling conditions) on tool wear, minimizing the number of expensive and time-consuming tool wear tests. Image 1 • Development of an algorithm for tool geometry updating. • Tool wear simulation in drilling with tool geometry update. • Analysis of tool wear effect on machined surface. • Simulation of cryogenic cooling and conventional metal working fluids. • New procedure combining numerical and analytical models in one strategy. [ABSTRACT FROM AUTHOR]

In the paper a numerical comparative analysis of stresses in a steel die com-pressed by a ring during the extrusion process was presented. In the research, three design solutions of the die were used. The solutions vary depending on the quotient of the wall thickness of the die insert and the wall thick-ness of the compression ring while maintaining a constant tool diameter. The stresses occurring in the areas of the ring and the die were calculated depending on the design version of the tool and the pressure value. The anal-ysis was carried out for the quotients of the die wall thickness to the ring wall thickness of 0.57, 1 and 1.75 and three press-in values of 0.004, 0.008 and 0.016 mm. The conducted research allowed determining the impact of the die design and assembly interference on the load bearing capacity. It was discovered that the use of a die insert with a smaller thickness com-pared to the thickness of the compression ring was the most advantageous from the point of view of the circumferential stresses.

The submitted paper deals with the simulation of thermal cycles during laser welding of aluminum sheets using Finite Element Method (FEM). After the design and creation of the simulation model, the simulation results were verified by the thermal cycles measured during the experiment on real samples. Verification has shown that, despite the differences that have resulted from some simplifications, the proposed model corresponds to the actual behavior of the material used during the laser welding process.

A new terrestrial gravitational wave detector, Superconducting Omni-directional Gravitational Radiation Observatory (SOGRO), has been proposed in 2016 and seen as a competitive candidate of middle-frequency gravitational wave detector. In this detector, there are three pairs of 5-ton low-temperature superconducting test masses separated by 30–50 m and magnetically levitated by superconducting coils carrying persistent currents. To get a sensitivity of 10− 19 − 10− 20Hz− 1/2, the levitation frequency of the test masses need to be as low as 0.01 Hz. Because of the machining and assembling errors, the levitation coil will tilt with respect to gravity and deviate from the center of the levitation coil. Alignment coils can cancel the tilt but bring extra stiffness to the test mass that enlarges the frequency. We numerically have studied a downscaled prototype of the superconducting magnetic levitation of SOGRO and find a possible design of the superconducting levitation system, which can reduce the levitation frequency to less than 0.01 Hz without increasing any hardware and complexity of the system. This study will benefit the development of SOGRO and other superconducting levitation devices. [ABSTRACT FROM AUTHOR]

Solid municipal waste (MSW) management is solved differently in many countries around the world, given their degree of development. There are countless systems for collecting, transporting and storing collected waste. Most machines for MSW collection are equipped with pre-compaction and compaction systems to reduce the volume of waste and transport a larger quantity over distances that often do reach several tens of kilometers. Vehicles for the collection and transport of waste are equipped with complex systems comprising: loading of containers, taking over and precompacting the material, compacting in the body of the structure and finally unloading in warehouses of the collected waste. Compacting is the process by which the volume of waste is reduced and this occurs through movements of the active organs and waste, in a complex structure located on the autochassis. The equipment is designed to collect / compact and transport in an economical and sanitary safety, pre-collected waste in generators. [ABSTRACT FROM AUTHOR]

Drawing process represents a significant area of production technology since it influences the feasibility of producing auto-body die panels. In the drawing process, the plastic deformation of blank is not uniform due to the intermittent deformation behavior of the material. This primes a non-uniform thickness distribution in the formed panels, which directly affects the die life and the quality of panels. In the presented study, a new algorithm was proposed for constructing the numerical control machining tool path for the new die surface obtained from FEM simulation and mesh mapping. The commercial package LS-DYNA was employed for the FEM simulation and to calculate the thickness distribution in the drawn workpiece. In order to construct the new numerical control machining tool path according to the new die surface, the positions of all cutter location points relative to the movement of new die mesh were determined. A set of forming die was machined using the proposed algorithm to fabricate a real workpiece of steel DC04. A comparison between the measured thicknesses in the fabricated workpiece and the FEM simulation results shows that they agree with each other very well, which directly validates the proposed algorithm. The developed method can improve product quality, increase production efficiency, and reduce labor intensity. [ABSTRACT FROM AUTHOR]

Vertical loads are commonly transferred by piles primarily in the upper structures. However, lateral loads are also significant compared with vertical loads in pile foundation design. Compared with a pile on level ground, there are many particular characteristics in a pile that is on sloping ground. These characteristics depend on the combined loading and the magnitude of the soil lateral displacement. In order to investigate the pile's bearing characteristics, a model test was conducted and ABAQUS software was adopted to conduct 3D numerical simulation of a single pile with different slope angles under combined loads. The experimental results indicated that (1) the soil pressure along the slope direction was smaller than the other side, resulting in an asymmetry of the slope soil around the pile, and in turn introducing a horizontal thrust to the pile; (2) with the increase of slope angle, the horizontal thrust increased while the single pile's bearing capacity decreased; (3) the vertical load caused more pile horizontal displacement with the growth of slope angle; and (4) the pile's moment and the displacement also increased with the growth of the slope angle. The findings in this study can provide a useful reference in the design of piles or anti-slide piles in sloping ground. [ABSTRACT FROM AUTHOR]

Laser shock forming (LSF) is an emerging method for metal sheet forming, and it can also be used to adjust the curvature of the curved metal. A series of laser shock adjustment experiments were conducted on 1-mm-thick curved aluminum 6061-T6 sheets using pulsed Nd3+:YAG laser operating at 1064-nm wavelength. The effects of various factors on the curvature adjustment were studied, including laser energy, impacted area, coverage rate of laser spots, and initial sheet shape. The mechanisms of curvature adjustment by LSF were studied by FEM simulation. The results have shown that the stress gradient mechanism and the shock bending mechanism were responsible for the two different kinds of deformation. The characteristic difference between the two mechanisms lies in whether the plastic deformation is directly induced on the bottom surface when the laser-induced shock wave is transmitted to the bottom surface. The curvature of the metal sheet can be adjusted conveniently within a certain range by changing the laser processing parameters, which is very useful for the engineering application. [ABSTRACT FROM AUTHOR]

A shear mode piezoelectric energy harvester for harvesting energy from rotary motion is developed. The kinetic energy in the form of rotation is converted into electrical form of energy by piezoelectric principle with oscillation of piezoelectric patch through magnetic shear force. Efforts have been made to increase the output power using shear mode of operation. In order to estimate the induced voltage of piezoelectric patch, a mathematical model and an Finite Element (FE) model are developed. Considering various parameters, optimization of the harvester was made. Analytical and Finite Element Method (FEM) results are compared and good agreement has been found. The total average output power of 358.44 W is generated when rotary speed of hub of about 600 RPM. [ABSTRACT FROM AUTHOR]

The fatigue life curves of materials are very sensitive to the magnitude of the stress amplitude. A small change or inaccuracy in the determination of the stress value causes large changes or inaccuracies in the calculated fatigue life estimate. Therefore, the use of computer simulations for fatigue life estimation requires a proper model development methodology. The paper is devoted to the problem of the modeling of components in notches using FEM. The modeling parameters significantly influencing the obtained stress results have been defined. Exact analytical solutions served as a benchmark for comparing the accuracy of the stress values obtained using FEM models. For the selected 2D and 3D notched components, diagrams were created for sensitivity analysis of the influence of the mesh element density at the root of the notch in correlation with the exact analytical solution. The findings from model building were applied to model the stress concentration at the root of a V-weld joint in a gas pipeline.

In the detection of small size mass loading, such as a single cell, a micro droplet or an aerosol particle, the sensors with longitudinally coupled surface acoustic wave resonator (LC-SAWR) structure can hardly avoid waveform distortions. The relative size of mass loading to the sensitive surface of the detector is the main factor affecting the response of LC-SAWR. The smaller the relative size, the worse the waveform distortion. In order to avoid influences from the mass loading’s size, in this paper, a transversely coupled SAW resonator (TC-SAWR) was proposed in order to achieve high performance in sensing small size mass loadings. For the design and simulation of TC-SAWR, the two-dimensional coupling of model (2D-COM) theory and finite element method (FEM) were used in this work. In the experiment, SiO2 was deposited on the sensor’s surface as a small size mass loading. The results from simulation and experiment mutually demonstrated the advantage of TC-SAWR to conquer waveform distortion in the detection of small size mass loading.

In the manufacture squirrel-cage rotors of asynchronous motors, a high standard of quality is required in every part of the production cycle. The die casting process usually creates porosity in the rotor bars. This most common defect in the rotor often remains hidden during the entire assembly of the machine and is usually only detected during final testing of the motor, i.e., at the end of the production process. This leads to unnecessary production costs. Therefore, the aim is to conduct a continuous control immediately after the rotor has been cast before further processing. In our paper, we are interested in selecting a suitable method of offline rotor diagnostics of an asynchronous motor that would be effective for these needs. In the first step, the selection of the method and its integration into the overall manufacturing process is carried out. The arrangement of the sensors and their calibration is then simulated on a 2D Finite Element Model of the rotor. The proposed offline measurement procedures and technologies are finally validated by testing measurements on a rotor that simulates the most frequently occurring faults. A test system is also developed that provides the operator continuous information about the running rotor measurements and makes it easier to evaluate the quality of the cast rotor by means of graphical visualization of the faults.

Magnetic fluid hyperthermia has gained much attention in recent years due to its potential in cancer treatment. Magnetic fluid is a colloidal liquid made of nanoscale magnetic particles suspended in a carrier fluid. The properties of a commercial magnetic fluid consisting of maghemite (γ-Fe2O3) particles suspended in mineral oil were used in the scope of our research. The paper deals with a novel approach to the development of a magnetic fluid FEM model of a laboratory setup, with consideration of the electromagnetic steady state and thermal transient calculation soft coupling. Also, adjustment of the mathematical model was added in such a way that it enables a link between the magnetic and thermal calculations in commercial software. The effective anisotropy’s influence on the calculations is considered. The simulation was done for different magnetic field parameters. The initial temperature was also varied so that a direct comparison could be made between the simulation and the measurements. A good indicator of the accuracy of the simulation are the SAR values. The relative differences in SAR values were in the range from 4.2–24.9%. Such a model can be used for assessing the heating performance of a magnetic fluid with selected parameters. It can also be used to search for the optimal parameters required to design an optimal magnetic fluid.

• A simple method is proposed to obtain section resultant forces in 2D elements based on an interpolated stress field. • A novel membrane element is investigated in simulations of reinforced concrete shear walls. • Using 2D membrane elements with coarse mesh grids to model wall structures is possible. Numerical simulation of reinforced concrete (RC) shear walls is a challenging task, due to the intricate underlying mechanics and the difficulty in balancing computational cost and accuracy. In the previous work, a general–purpose four–node quadrilateral drilling element named as GCMQ has been developed by the authors. This new element performs well with coarse meshes and provides engineers an option to efficiently simulate planar problems, such as shear walls subjected to in-plane loadings. Meanwhile, GCMQ can recover nonlinear distribution of stress field so that section resultant forces can be explicitly integrated. In this paper, GCMQ is validated via numerical simulations of several RC shear wall specimens with different reinforcement schemes and geometries. Compared to experimental results, numerical models show that GCMQ can accurately simulate in-plane response such as pushover backbones with a relatively low cost for both short and slender walls. With proper material models, it is also possible to recover other quantities such as damage distribution patterns. Since GCMQ is essentially a microscopic finite element, convergence is guaranteed, local response can also be obtained with mesh refinement. GCMQ could be used as a good tool for future modelling of shear walls and similar structures. [ABSTRACT FROM AUTHOR]

High-pressure jet coolant assistance was used in the cutting process of Inconel 718. The effects of coolant pressure on cutting force and machined surface quality were researched. As well as the experimental design, Two-dimensional cutting models for Inconel 718 were established using AdvantEdge FEM software. Simulations and experiments were carried out based on the Taguchi method. The simulation predictions and experimental test results were compared. The influence of variables on cutting force and machined surface roughness was determined by variance analysis. The effect of cooling pressure on roughness of machined surfaces was studied by simulation and experiment tests. [ABSTRACT FROM AUTHOR]

It is well known that high thermal stresses in the formed parts during selective laser melting (SLM) heavily affect the part quality and performance. In this study, the mechanism of thermal stress formation due to temperature gradients in SLM of 316L stainless steel is investigated. The uniqueness of this study lies in the fact that a realistic multi-track and multi-layer SLM process is modeled and simulated that adopts the identical conditions of the actual part building on a commercial SLM system, and the final residual stresses are compared between the simulation and the experimental measurements on the actual parts. The results indicate that both temperature and stress evolution of material points exhibit cyclic patterns during the SLM process, and the changes with regard to time are dramatic thanks to the rapid heating and cooling of localized areas. However, the rapid temperature decrease is actually accompanied by stress increase in the material points, and vice versa. Under the laser power of 160 W and scanning speed of 500 mm/s, a melting pool is formed and rapidly expanded to the adjacent pre-solidified layer, and the diffusion depth is about 200 μm. Also, unlike the overall attenuation of temperature as the SLM build process progresses, the magnitude of stress oscillation actually increases. Furthermore, during the rapid solidification, the core of melting pool is subject to tensile stress. The tensile stress could be partially mitigated by the laser heating of subsequent layers, but it cannot be completely removed. As a result, the accumulation effect of multiple layers leads to significant tensile stress, in particular, in the bottom layers that are closer to the base plate. The effective stress in the bottom layer attached to the base plate reaches as high as 680 MPa based on the settings of SLM process. Finally, the experiment measurement on residual stress overall agrees with the simulation results. Both show that the residual stress ranges from 100 to 350 MPa for the layers 1.4 mm above the base plate, and that the tensile stress tends to increase along the direction towards the base plate. [ABSTRACT FROM AUTHOR]

The purpose of this manuscript is to carry out an experimental and numerical investigation of bulging process of aluminum AA1050-H14 sheet metal in free expansion when using a flexible punch. Three types of rubber with different hardness are used as flexible punch. First, a mechanical characterization and identification of aluminum sheet metal and polyurethane rubber parameters is achieved for validation purpose. Then, an experimental study of flexible bulging process is performed to analyze the effect of rubber type and hardness on forming capability. The obtained results show that the polyurethane with hardness of 70 Shore A is considered as the most suitable punch for the bulging operation when comparing with silicone and natural rubber. Finally, a comparison between bulging with flexible and rigid punches is conducted using the finite element code ABAQUS/Explicit. The developed simulations predict efficiently the realistic thickness distribution along the bulged part. [ABSTRACT FROM AUTHOR]