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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]

We present a holistic approach for the photovoltaic (PV) module frame improvement that considers mechanical, electrical, economic, and ecological aspects for different frame designs. In a comprehensive study, the approach is applied to exemplary PV module frame designs. The analyses performed in this study show a potential improvement path of the module frame design. This leads to an overall better module performance and helps finding the balance point between technical performance, cost, and environmental impact. Based on the results, the PV module frame design affects the aspects analyzed in this work differently. For the comparison, we defined reference frame design with 16 and 20 mm front and rear frame widths. The improvement is reached by unitizing the frame width for both sides to 18 mm and increasing its cavity width to 12 mm instead of 8.5 mm. Tuning the frame parameters in this way leads to the best balance point for frame designs in this study regarding all aspects. The mechanical finite element method (FEM) simulation results show that even a small change on the frame width has a significant influence on the stress within the solar cells. Compared with the reference frame, the optimized frame design shows 2.6% less deflection, which corresponds to around 0.7 mm. Cell‐to‐module (CTM) analysis shows that a bigger frame width lightly decreases the cover coupling power gain. Results show that increasing the front frame width from 16 to 20 mm reduces the module power by about 0.12 WP. Findings of the cost of ownership (COO) analysis suggest that the optimized frame can save around 30 g aluminum which reduces the total module cost by 0.1%. Life cycle assessment (LCA) results are directly correlated to the material mass of the corresponding design. Results show that using the optimized frame can save 0.8 kg CO2‐eq/kWP due to the saving in aluminum compared with the reference frame. [ABSTRACT FROM AUTHOR]

This paper aims to develop a new forming technique to manufacture a long semihollow stepped part. Traditionally, hot backward extrusion is used, but this technique is not suitable because it requires a very high forming load to act on the die and punch, especially at the contact between the punch and workpiece. As a result, the service life of the punch is very low. Therefore, a new technique to overcome this problem is needed. A combined bulging–piercing technique was proposed and developed in this research. The main concept of this technique is to bulge the part by upsetting the workpiece between the punch and counterpunch to generate high frictional contact pressure, which will help to restrain the material from sliding down into the die cavity during the piercing step. In other words, this technique utilizes frictional force at the die–workpiece interface to reduce the forming load of the punch. Finite element modeling was employed to investigate and determine a suitable level of the bulging which can reduce the forming load without generating any significantly high force to the counterpunch. Only experiments with the minimum forming load were selected and implemented to validate this concept because other conditions with high load will risk damaging the punch and machine press of the product line. The results show that this technique can reduce the forming load by almost 40% and also control a good concentricity of the part and reduce the wall thickness variation. [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]

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]

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Accurate modeling or simulation of the vehicle-terrain interaction is critical for effective off-road vehicle navigation. While several high-accuracy methods exist (for example FEM simulation) they typically require computational capacity that exceeds what can be installed in a vehicle. Therefore, they are not applicable for real-time off-road vehicle navigation purposes, where computer hardware capacity is limited by the need for onboard installation. To address this challenge, simplified and less detailed models must be developed for real-time applications. This paper compares three different two-dimensional static terrain-vehicle models, considering accuracy and computational capacity requirements. Results of the comparison provide insights into the suitability of each model for real-time navigation of off-road vehicles. [ABSTRACT FROM AUTHOR]

In recent years, FEM (Finite Element Method) simulation has been commonly used in the design field; FEM simulation can be classified into static implicit and dynamic explicit methods. In particular, static implicit FEM simulation is very commonly and usefully used in industry. In machine tool design, FEM thermal simulation is also used to develop high-precision machine tools. However, the phenomenon of heat build-up in the machine tool structure and the analysis of forced air intake and exhaust by a fan to the machine structure are difficult to be analyzed by FEM thermal simulation. Therefore, in this study, four virtual models for air intake, exhaust air, heat transfer and convection were developed, and the analysis methods for the phenomenon of heat build-up and forced intake and exhaust air were developed and evaluated. As a result, it was concluded that (1) the phenomenon of heat build-up in the structure and forced intake and exhaust to the structure can be analysed, (2) the FEM thermal analysis with the four developed virtual models has high calculation accuracy and short calculation time, and (3) the proposed method is very effective in the design.

As one of the most important components of a vehicle, the automotive coating system is typically a multi-layer polymeric structure with complex scratch damage patterns. This work is the first one to systematically investigate the scratch performance of an automotive coating system via experimental and numerical approaches. To achieve this end, uniaxial tensile tests are firstly carried out to acquire the basic mechanical properties of paint films at different strain rates. Then, a series of scratch tests are conducted in accordance with ASTM D7027/ISO 19252 standards, and the damage features are identified. In addition, the effects of scratch speed, loading rate, and stylus type are experimentally investigated. Afterwards, a finite element approach for scratch simulations is developed, which includes a rate-dependent constitutive model calibrated using the uniaxial tensile tests, a tied interface algorithm for efficient connection between coating and substrate, and an interior contact method to avoid excessive element distortions. Eventually, with the aid of the presented numerical approach, the damage patterns observed in scratch tests are numerically explained, and the scratch damage process is reasonably surmised. The presented approaches and findings can contribute to the development of anti-scratch automotive coating structures.

The first-step drawing process of the platinum-clad nickel composite bar was numerically simulated using DEFORM 3D finite element analysis software. The Taguchi method was used to study the effect of the first-step drawing parameters (the semi-angle of die α, the friction coefficient between the platinum tube and die μ1, the friction coefficient between the platinum tube and nickel rod μ2 and the outer diameter of the original platinum tube D) on the effective stress of platinum-clad nickel bar. Then, the optimal combination of parameters (D = 7.55 mm, μ1 = 0.2, μ2 = 0.3, α = 3°) was obtained. Furthermore, the results of the deformation behavior, cladding behavior, stress effectiveness and the distribution of the damage of the composite bar using optimization schemes were compared and analyzed with Numerical Simulations 8, which showed the worst result. Meanwhile, the experimental results were in general agreement with the simulation results of optimal combination of parameters, indicating that our simulation results are plausible. This has certain guidance significance to improve the quality of platinum-clad nickel composite wires in actual production.

• Comparison of long and short intramedullary nails for the stabilization of different reverse pertrochanteric fracture patterns. • No significant biomechanical differences between long and short nails. • Fracture stability decreases with distal fracture extension. • Fracture stability decreases with decreasing bone quality. There is currently no definitive evidence for the implant of choice for the treatment of reverse pertrochanteric fractures. Here, we aimed to compare the stability provided by two implant options: long and short intramedullary nails. We performed finite element simulations of different patterns of reverse pertrochanteric fractures with varying bone quality, and compared the short vs long nail stabilization under physiological loads. For each variable combination, the micromotions at the fracture site, bone strain, and implant stress were computed. Mean micromotions at the fracture surface and absolute and relative fracture surface with micromotions >150 µm were slightly lower with the short nail (8%, 3%, and 3%, respectively). The distal fracture extension negatively affected the stability, with increasing micromotions on the medial side. Bone strain above 1 % was not affected by the nail length. Fatigue stresses were similar for both implants, and no volume was found above the yield and ultimate stress in the tested conditions. This simulation study shows no benefit of long nails for the investigated patterns of reverse pertrochanteric fractures, with similar micromotions at the fracture site, bone strain, and implant stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two innovative strategies have been proposed to protect energy harvesters with frequency up-conversion mechanism from mechanical overload. • Finite element method has been used to model and analyse the proposed protection strategies. • Experiments have been conducted to verify the strategies and modelling. • The capability of protecting the harvesting device from unexpected overload is demonstrated. • The protection mechanisms and damping effects of the proposed strategies are discussed. Vibration energy harvesters utilising the frequency up-conversion mechanism have been effective in harvesting low-frequency ambient vibrations. However, the mechanical impact required for this process could also damage the devices when excessive load is applied. To address this issue, this paper presents novel protection strategies for energy harvesters with a frequency up-conversion mechanism, including a ring-type stopper within the resonant system and specially designed impact protection components (IPC) within the impact system. By applying these methods, the influence of excessive input excitation has been mitigated, and thus, the reliability and durability of the device have been improved. Finite element modelling has been employed to model the proposed protection methods, and then experiments have been conducted to verify and refine the modelling. Stress analysis is finally conducted based on the refined model to validate the effectiveness of the protection strategies. The results demonstrate that the proposed strategies are capable of protecting the harvesting system from excessive input excitations, which means the device functions effectively in the operating state and decelerates the growth rate of maximum stress and acceleration in the limiting state. This research contributes valuable insights into the development of effective protection strategies for energy harvesters with frequency up-conversion mechanisms, thereby improving their durability and performances in real-world applications. [ABSTRACT FROM AUTHOR]

A number of industrial applications today require thermally sprayed coatings that exhibit good adhesion, high temperature and chemical resistance, and can withstand particle impacts or dynamic interactions with components. A common example of a high-velocity oxygen fuel (HVOF) sprayed coating with such the aforementioned properties is Cr 3 C 2 –25%NiCr. The objective of this study is to examine the impact of varying thicknesses and surface roughness on the impact lifetime and impact wear of Cr 3 C 2 –25%NiCr coatings. A series of Cr 3 C 2 –25%NiCr coatings were subject to analysis using a dynamic impact tester with impact loads of 200 N, 400 N, and 600 N. The results indicated that there exists an optimal coating thickness with the highest impact lifetime. The results were discussed using microstructural analysis of the impact coatings and finite element simulation. The maximum impact lifetime was achieved with the optimal combination of sample material properties, substrate mechanical properties, coating thickness, and residual stress. Furthermore, it was demonstrated that surface does not influence the impact lifetime of the coating, but does affect the accuracy of its determination. • Impact lifetime of Cr 3 C 2 –25%NiCr coatings with various parameters was investigated. • The impact behaviour was discussed using structural analysis and FEM simulations. • Internal cohesion failure occurred before surface cracking was visible. • A local maximum of the impact lifetime was found at the optimal coating thickness. • The surface roughness affects the precision of impact lifetime evaluation. [ABSTRACT FROM AUTHOR]

This article presents a research study involving different simulations of crash tests by means of the finite element explicit dynamic software Ansys LS-Dyna to determine the roadworthiness of a fully composite chassis lightweight solar vehicle and its conformity to the World Solar Challenge (WSC) regulations. Furthermore, the paper describes the results of crash test simulations in conditions comparable with those of the standard homologation test, with an initial velocity of 15.5 m/s against a rigid barrier considering overlaps of 50% and 100%. The velocity measured at the base of the seat was later used in a sled test with a dummy to calculate the Head Injury Criterion (HIC), a number proportional to the probability of head injury caused by the impact. The values remained within the threshold of acceptability with overlap at 50% but exceeded the limit with the 100% overlap. With no load limiter implemented in the model, the seatbelt caused contact forces with the chest up to 14 kN against 6 kN of the typical load limiter used in road cars to limit damage to ribs and internal organs. Finally, the possibility of improving the front crash box was investigated by changing the crash box's planar sandwich structure with corrugated ones and layup without foam between the carbon layers. Various values of semi-amplitudes (A) of the sinusoidal profile have been tested. With a value of A of 6 mm, the capacity to absorb energy from an impact at 9 m/s was close to the original configuration. [ABSTRACT FROM AUTHOR]

A finite element method (FEM) for simulating seismic wave fields of three-dimensional (3D) local irregular topography is proposed in this article. The author begins by developing a program to solve the seismic response of 3D layered foundations using the frequency-domain stiffness matrix method. This enables the user to easily obtain the input of ground motion for the finite element model, as well as conduct finite element simulations of the seismic wave field of incident P-, SH-, SV-, and Rayleigh waves coming in from any direction. This method solves the problem that previous 3D finite element modeling methods couldn't handle SV waves when the angle of incidence is greater than the critical angle. Furthermore, it effortlessly accounts for the dispersion properties inherent in layered foundations. A series of 3D seismic wave field simulation examples are employed to validate the method's accuracy. In the end, this method is subsequently applied to further investigate the seismic response of frame structures in sedimentary valleys, and the significance of soil nonlinearity and topographic effects on the seismic response of structures is presented. • A two-step FEM is proposed to study the seismic response of irregular terrain. • It is capable of simulating seismic waves coming in at any angle. • It works for body and surface waves and can consider wave dispersion. • It also applies to soil-structure interactions and nonlinearities. • Good accuracy of the method is presented, and topographic effects are verified. [ABSTRACT FROM AUTHOR]

In the detection of biomolecules, surface plasmon resonance (SPR) sensors require high sensitivity. In this study, we propose a sensitivity-enhanced functionalized plasmonic interface based on Ag–TiO 2 –Co(OH) 2 nanosheets structure. Compared to unmodified SPR sensors, the sensitivity of the sensor decorated with TiO 2 and Co(OH) 2 nanosheets is increased by 130.84%, reaching 5764.27 nm/RIU. This enhancement is attributed to the high refractive index of the coating, as well as the high specific surface area and abundant active sites provided by the synthesized Co(OH) 2 nanosheets with a multi-grooved structure. Additionally, employing a double-antibody sandwich method, the antibody-functionalized plasmonic interface enables specific detection of human serum albumin (HSA). The linear response of this sensor was in the wide range of 0.4–150 μM, and the LOD reached 154.89 nM(K D is approximately 1.73 × 10−6 M). This novel SPR sensor offers a new strategy for biochemical sensing and provides a highly sensitive platform for immunoassays. [Display omitted] [ABSTRACT FROM AUTHOR]

Transcranial ultrasound stimulation (TUS) is a young neuromodulation technology, which uses ultrasound to achieve non-invasive stimulation or inhibition of deep intracranial brain regions, with the advantages of non-invasive, deep penetration, and high resolution. It is widely considered to be one of the most promising techniques for probing brain function and treating brain diseases. In preclinical studies, developing miniaturized transducers to facilitate neuromodulation in freely moving small animals is critical for understanding the mechanism and exploring potential applications. In this article, a miniaturized transducer with a half-concave structure is proposed. Based on the finite element simulation models established by PZFlex software, several ultrasound transducers with different concave curvatures were designed and analyzed. Based on the simulation results, half-concave focused ultrasonic transducers with curvature radii of 5 mm and 7.5 mm were fabricated. Additionally, the emission acoustic fields of the ultrasonic transducers with different structures were characterized at their thickness resonance frequencies of 1 MHz using a multifunctional ultrasonic test platform built in the laboratory. To verify the practical ability for neuromodulation, different ultrasound transducers were used to induce muscle activity in mice. As a result, the stimulation success rates were (32 ± 10)%, (65 ± 8)%, and (84 ± 7)%, respectively, by using flat, #7, and #5 transducers, which shows the simulation and experimental results have a good agreement and that the miniaturized half-concave transducer could effectively converge the acoustic energy and achieve precise and effective ultrasonic neuromodulation. [ABSTRACT FROM AUTHOR]

The aim of the article is to present a new idea of limiting the bearing voltage in electric machines with permanent magnets through the use of a shielding winding placed in stator slot wedges. The first part of the article is dedicated to the mechanisms of generating bearing voltages when the machine is supplied from the mains and from a power electronic converter. Additionally, some methods of counteracting these phenomena were described. Next, multivariant simulation tests were carried out based on the two-dimensional field model of a synchronous machine with permanent magnets. The tests were run in order to determine the internal capacitances of the machine, on which the level of bearing voltages depends. Based on these results, the optimal variant of the design solution ensuring the limitation of the bearing voltage to a safe level was selected. Using the model of a two-level converter and based on the equivalent diagram of the internal capacitances of the machine, the influence of the proposed shielding winding on the bearing voltage was estimated. [ABSTRACT FROM AUTHOR]

Embossing is a converting process in which the surface of a tissue paper sheet is changed under high pressure, allowing different functions. In this work, the authors intend to study how the embossing pressure affects the main properties of tissue paper, using a laboratory embossing system. An optimum pressure was achieved at 2.8 bar to this embossing laboratory set-up. The effect of pressure when densifying the paper sheet gives it a gain in mechanical strength but no differences in terms of liquid absorbency. The two embossing patterns present different behaviors but both evidence losses in mechanical and softness properties. On the other hand, the finite element method (FEM) does not show clear evidence of how the pressure affects the paper strength. For the deco die, it is possible to observe that the amount of yielding is slightly higher for lower pressure (2.4 bar), but this plasticity state parameter is very similar for 2.8 bar and 3.2 bar. For the micro die, FEM simulations of the manufacturing pressure do not show a considerable impact on the amount of plasticity state of the material; only for 3.2 bar, it shows a change in the pattern of the plasticity state of the paper during the embossing processes. In the end, to achieve a final product with excellent quality, it is important to make a compromise between the various properties. [ABSTRACT FROM AUTHOR]

The embossing operation is one of the processes of tissue paper converting. The embossing parameters influence the final properties of tissue products, such as mechanical, softness, and bulk. In this study, the influence of the rubber hardness used against the embossing steel rolls with a pattern created by intaglio engraving was studied. Three different configurations of rubber plates stacking, each plate with different hardness, were studied. After embossing, mechanical properties, softness, and bulk were evaluated to analyze the effect of rubbers hardness on these properties. Furthermore, a Finite Element Model of the embossing operation was used that considered the same rubber plates stacking configurations used in experiments, and it was able to replicate the experimental results. This work led us to conclude that the configuration where two rubber plates with different hardness, where the rubber plate with higher hardness is in contact with the tissue paper sheet, has shown to be the best solution to obtain higher softness. These findings support the use of embossing operations rubber rolls with a low hardness internal layer and a high hardness external layer in industry. Thus, finite element models were also shown to be reliable tools to virtually test other configurations, such as, for example, three or more rubber plates with different hardness. Since embossing is one of the tissue paper transformation operations with the greatest impact on the key properties of the final product, this study allows the producer to optimize them by varying the hardness of the rubber roll, as well as its configuration. [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]

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. [ABSTRACT FROM AUTHOR]

The grind-hardening process aims to increase the surface hardness of the material through the dual action of the mechanical and thermal load. A novel approach to model the process and predict the hardness penetration depth was developed based exclusively on the prediction of austenite-martensite transformation. A combined micro and macro scale approach was implemented to forecast the temperature reached in the surface starting from the action of a single grain and using its specific cutting power to design a moving heat source representing the interaction between the grinding wheel and the material. The martensitic transformation temperature considered in this paper takes into consideration the fast heat cycle typical of this process. In order to validate the model, tangential surface grinding tests were performed on 42CrMo4 and microstructural analysis with micro-hardness measurements were performed. This research presents a first step in developing a grinding process simulation that includes multi-grain grinding, real grain geometries, binder effect, and real workpiece-grinding wheel kinematics. [ABSTRACT FROM AUTHOR]

Transcranial ultrasound stimulation (TUS) is a young neuromodulation technology, which uses ultrasound to achieve non-invasive stimulation or inhibition of deep intracranial brain regions, with the advantages of non-invasive, deep penetration, and high resolution. It is widely considered to be one of the most promising techniques for probing brain function and treating brain diseases. In preclinical studies, developing miniaturized transducers to facilitate neuromodulation in freely moving small animals is critical for understanding the mechanism and exploring potential applications. In this article, a miniaturized transducer with a half-concave structure is proposed. Based on the finite element simulation models established by PZFlex software, several ultrasound transducers with different concave curvatures were designed and analyzed. Based on the simulation results, half-concave focused ultrasonic transducers with curvature radii of 5 mm and 7.5 mm were fabricated. Additionally, the emission acoustic fields of the ultrasonic transducers with different structures were characterized at their thickness resonance frequencies of 1 MHz using a multifunctional ultrasonic test platform built in the laboratory. To verify the practical ability for neuromodulation, different ultrasound transducers were used to induce muscle activity in mice. As a result, the stimulation success rates were (32 ± 10)%, (65 ± 8)%, and (84 ± 7)%, respectively, by using flat, #7, and #5 transducers, which shows the simulation and experimental results have a good agreement and that the miniaturized half-concave transducer could effectively converge the acoustic energy and achieve precise and effective ultrasonic neuromodulation.

The welding process causes high local heat input on the material, which leads to microstructural changes in the base material, followed by the development of residual stresses in the welded components. This has a significant impact on the performance of the welding joint. Therefore, it is crucial to effectively predict the effect of temperature, metallurgical and structural changes on the component, which can be achieved by numerical simulation.The main goal of this work is to mathematically investigate the influence of thermo-metallurgical phase transformations on the welding residual stresses which was induced by laser beam welding in low alloy steel (S235JR). In this study, two separate numerical simulation models were analyzed using the software Abaqus CAE. One numerical model describes the thermo-mechanical behavior and the other describes the thermo-metallurgical-mechanical behavior of the system which was realized using UEXPAN user subroutine. In this user subroutine, the kinematics of phase transformation was computed using the modified Johnson-Mehl-Avrami and Kolomogorov while considering a nucleation and growth process that controls the dissolution of the initial microstructure. The generation of martensitic transformation has been accounted by the Koistinen-Marburger equation. In the next step, the phase transformation subroutine has been integrated with a structural model along with a special temperature step function to realize the effect of thermal strain and the strain caused by phase transformation on the welding residual stresses. The computed residual stresses of both the models were compared with the experimentally measured residual stresses using the hole drilling method. These results show that the inclusion of phase transformations has a significant effect on the residual stresses of the welded component.

Bulb turbine units are one of the most installed turbines in run-of river projects with relatively low head. In order to enlarge the useful life of these turbines and avoid fatigue problems and cracks, it is of paramount importance to understand and determine the most relevant parameters and their influence on the dynamic response of the structure. In this paper, the modal characteristics of a bulb turbine unit in operation is numerically investigated, considering the rotation effect. A FEM model including alternator, shaft, runner and fluid is developed and the boundary conditions are determined. Firstly, the modal characteristic of the runner under different blade opening are analyzed. Then the influence of the rotation on the modal characteristic of the shaft and runner is discussed. The numerical method is verified by comparing with experimental results of a rotating and submerged disk. The results show that the runner modes are mainly blade-modes，which can be grouped according to the blade number, one jellyfish mode and four local modes in each group. A modified Campbell diagram of the global modes and a transformation matrix of natural frequency between dry modes and wet modes are proposed. Results of this study helps to understand the most influencing parameters, such as the added mass effect of water combined with the rotation. The proposed modified Campbell diagram could be used for an accurate calculation of natural frequencies and avoid possible resonance problems in future designs of bulb turbine units. [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]

The filling stage is a critical phenomenon in sand casting for making reliable castings. Latest research has demonstrated that for most liquid engineering alloys, the critical meniscus velocity of the melt at the ingate is in the range of 0.4–0.6 m s−1. The work described in this research paper is to use neural network (NN) technology to propose digital twin approach for gating system design that allow to understand and model its performances faster and more reliable than traditional methods. This approach was applied in the case of sand casting of liquid aluminum alloy (EN AC-44200). The approach is based first on a digital representation of filling process to perform the melt flow simulations using a combination of the gating system design parameters, selected as a training cases from Taguchi orthogonal array (OA). The second step of the approach is the data capture of functional gating design system to train up the feed-forward back-propagation NN model. The validation of the well-trained NN model is assessed by interrogating predicted ingate velocity to it and making reliable predictions with high accuracy. The claim is that such digital twin approach is an effective solution to recognize the functional design parameters from the entire filling systems used during casting process. [ABSTRACT FROM AUTHOR]

Equal Channel Angular Pressing (ECAP) is one of the most innovative Severe Plastic Deformation (SPD) methods used for grain refinement of materials up to ultra-fined or Nano structured level which leads to superior mechanical properties. Computer simulation is one of the best alternative of actual ECAP deformation to know the influence of each processing parameters on end results. In the present work, AA2024 alloys is used, which is a demanding material in aircraft structure and automotive applications. To understand the process/die design parameter, 3D FEM simulation is done on ECAP process using DEFORM-3D software. Simulation was done on different channel angles such as 90º, 105º, 120º and 135º and corner angles such as 0º, 10º, 20º and 30º. The ECAP process was simulated for a single ECAP pass. The results concern to the extrusion load, developed stresses, effectivestrain and temperature variation on the processed material were noted obtained. From the observed results, it was found that the minimum channel angle produces the maximum temperature profile on the material, develop maximum stress and strain at deformation zone. Additionally, the outcome acquired by such computational technique illustrate that the shear strain decrease with increase in channel and corner angle. [ABSTRACT FROM AUTHOR]

Unlike the Almen control available for shot peening, no controlling solutions are proposed for laser shock processing at the industrial level to relate the processing parameters to results. This may cause time loss in preparing the convenient parameters to obtain desired results. The current work presented experimental and numerical studies evidencing the possible application of the Almen control in laser shock processing, where the exposition time considered in shot peening is substituted by the laser pass repetitions. C75 Almen-like strips of type "A" and "C" are used in this work. The obtained results confirmed the idea that laser shock evidence a saturation trend with laser pass repetitions. This trend was investigated by Almen gauges to measure strip curvatures and to deduce the Almen Intensities of the process parametrization. This finding demonstrated the possible extrapolation of the Almen control to laser shock processing allowing an easier parametrization at the industrial level. [ABSTRACT FROM AUTHOR]

Rare-earth substituted iron garnets (REIGs) are interesting materials which may present large in-plane magnetization. In correspondence of defects, domain walls (DWs) undergo nucleation, segmentation, and pinning. In such cases, the Néel spike domain structure may appear, and its DWs can produce not negligible stray fields above the REIG. Experimental characterization through quantitative magneto-optical imaging with an indicator film showed that stray fields are detectable above the surface of Lu and Bi substituted iron garnets in correspondence of DWs delimiting a Néel spike that is generated by a microcrack. These DWs are interesting for both fundamental studies and innovative applications, and therefore carrying out a quantitative analysis is crucial. To understand how the externally detected stray fields are correlated with the pattern of the internal magnetization, here we propose 2-D and 3-D models based on FEM developed through the COMSOL Multiphysics software. These models consider the in-plane magnetization of the REIG and the magnetic microstructure of the Néel spike. They provide a good reproduction of the magnetic fields and allow describing the corresponding magnetic microstructure. It turns out that the results are both in agreement with the experiments. [ABSTRACT FROM AUTHOR]

The acoustic emission (AE) technique has become a well-established method of monitoring structural health over recent years. The sensing and analysis of elastic AE waves, which have involved piezoelectric wafer active sensors (PWAS) and time domain and frequency domain analysis, has proven to be effective in yielding fatigue crack-related information. However, not much research has been performed regarding (i) the correlation between the fatigue crack length and AE signal signatures and (ii) artificial intelligence (AI) methodologies to automate the AE waveform analysis. In this paper, this crack length correlation is investigated along with the development of a novel AE signal analysis technique via AI. A finite element model (FEM) study was first performed to understand the effects of fatigue crack length on the resulting AE waveforms and a fatigue experiment was performed to capture experimental AE waveforms. Finally, this database of experimental AE waveforms was used with a convolutional neural network to build a system capable of performing automated classification and prediction of the length of a fatigue crack that excited respective AE signals. AE signals captured during a fatigue crack growth experiment were found to match closely with the FEM simulations. This novel AI system proved to be effective at predicting the crack length of an AE signal at an accuracy of 98.4%. This novel AI-enabled AE signal analysis technique will provide a crucial step forward in the development of a comprehensive structural health monitoring (SHM) system. [ABSTRACT FROM AUTHOR]

This study focuses on prediction of distortion behavior of multi-pass GMAW of structural offshore steel S460G2 + M using thermo-mechanical (TMM) and inherent strain (ISM) methods. In TMM, material properties including plasticity model were obtained from advanced material modeling software based on characterized elemental compositions and double ellipsoid heat source model is implemented. In ISM, residual plastic strain theory is developed based on initial strain value calculated in longitudinal and transverse direction. The predicted distortion and experiment values show an error margin within the range of 8% using TMM and 12% applying ISM with very low computation time. [ABSTRACT FROM AUTHOR]

Based on an analytical/numerical modeling approach, this paper details the derivation steps of both in-plane and out-of-plane universal sensitivity expressions of an efficient 3-axis convective accelerometer. The analytical modeling method uses finite element analysis to model the effects of key parameters on the sensitivity of the CMOS micromachined sensor. From the definition of the design space and biasing condition, the heater temperature and key geometric parameters of the sensor are swept in a wide range. Using numerical studies of a previously validated 3D Finite Element Model (FEM), the impact of each specific parameter on sensitivity is then extracted from simulation results. This method is applied to develop both in-plane and out-of-plane sensitivity expressions as a function of main geometrical parameters, which include the height and width of bottom cavity and top cover in addition to the heater temperature. FEM simulations are then used to validate the obtained compact analytical models of the sensitivities for a large range of feasible design parameters through CMOS technology. We obtain a maximum deviation of 9% between numerical and compact model results. Final expressions can be considered as a very useful guide when designing a 3-axis convective accelerometer for an early estimation of sensitivity levels. [ABSTRACT FROM AUTHOR]

• Cloth is modeled as an inextensible continuous surface. • The model is validated experimentally for robot manipulation purposes. • Inextensibility is modeled in a novel way without introducing locking. • Continuity allows the use of coarse meshes, drastically reducing simulation times. • The simulator can be used interchangeably with triangle or quadrilateral meshes. We introduce a new isometric strain model for the study of the dynamics of cloth garments in a moderate stress environment, such as robotic manipulation in the neighborhood of humans. This model treats textiles as surfaces that are inextensible, admitting only isometric motions. Inextensibility is derived in a continuous setting, prior to any discretization, which gives consistency with respect to remeshing and prevents the problem of locking even with coarse meshes. The simulations of robotic manipulation using the model are compared to the actual manipulation in the real world, finding that the difference between the simulated and the real position of each point in the garment is lower than 1cm in average even when a coarse mesh is used. Aerodynamic contributions to motion are incorporated to the model through the virtual uncoupling of the inertial and gravitational mass of the garment. This approach results in an accurate, when compared to the recorded dynamics of real textiles, description of cloth motion incorporating aerodynamic effects by using only two parameters. [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]

Ballast layer is the most weak element of railway track that causes track geometry deterioration. At the same time,it is subjected to intensive particle breakage during the corrective tamping. This causes high maintenance costs of ballasted track. The present paper is devoted to the study of tamping methods. The present machine tamping methods are considered and compared. The possible influence of the tamping technology on the ballast-related maintenance costs is analyzed. The side tamping technology is studied in detail with theoretical and experimental methods. The process of material transport during the side tamping is studied using a scale model of ballast layer and photogrammetric measurements. A theoretical finite element model (FEM) is validated to the experimental results. The study shows that the side tamping is a promising method for the development of a universal, superstructure independent tamping technology.

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.

In this research, a novel method of CVI + RMI 3DN C/SiC torque tube preparation has been researched. CVI + RMI 3DN C/SiC flat panel was evaluated by Archimedes drainage method for density and open porosity, SEM for morphological characterization, XRD for phase composition characterization, and chemical method for composition mass and volume content. It has an average density of 2.19 g cm ^−3 , and open porosity of 10%. The computed chemical composition method findings are undoubtedly in line with the fiber design volume percentage of 30%. Tensile and shear mechanical tests on 3DN C/SiC standard sample were investigated, with good performance. The average tensile and shear strength was 141.64 MPa and 86.24 MPa respectively. 3DN C/SiC torque tubes were prepared by the same process, and the torsional mechanical tests were carried out. According to the mechanical parameters of the flat panel 3DN C/SiC sample, the mechanical properties of stress distribution and shear stress-strain curves for the torque tube are predicted by using the finite element simulation method, which is in good agreement with the test results. The test and simulation error of the maximum shear strength is only about 2%.

The 2008 Mw7.9 Wenchuan earthquake ruptured northwest‐dipping imbricate oblique reverse faults along the Longmenshan thrust belt at the eastern margin of the Tibetan Plateau, and developed one of the most complex coseismic rupture patterns for reverse faulting events ever reported in intraplate settings. To evaluate to what extent complex fault geometry and heterogeneities in initial stress can explain the characteristics of coseismic observations, we simulate spontaneous dynamic rupture propagation governed by slip‐weakening friction law on the geometrically complex multifault system loaded by heterogeneous stress. Our model reproduces many observed features including the multifault ruptures, locations of the maximum slip, Interferometric Synthetic Aperture Radar observations, source time functions and peak ground velocities. Our results suggest that the maximum horizontal principal stress in the northern part of Beichuan Fault (BFC) is rotated approximately 6.5° counterclockwise compared to that in the southern part of BFC, yet this rotation is not sufficient to produce a supershear rupture. We infer that the fault core zone in the southwestern Beichuan Fault (BCF) may have been more severely damaged than the northeastern counterpart, which provides an explanation that the rupture in the northern BCF propagates faster than in the southern portion. Besides, we find that Coulomb failure stress changes on Wenchuan‐Maoxian Fault (WMF) may be counteracted by the aftershock slips of the Lixian Fault, which suggests Wenchuan earthquake could not significantly push the WMF closer to failure. Plain Language Summary: The 2008 Wenchuan earthquake caused great destruction to cities and counties along the northwestern margin of the Sichuan Basin. At least three faults slipped in this event, showing complex surface deformation. In this study, we develop a complex non‐planar multifault model containing heterogeneities tectonic stress, using computer simulation to reproduce dynamic rupture process of this event. The results derived from simulations are well consistent with many observed features, and help to explain why the zones near Yingxiu and Beichuan towns suffered the most intensive shock. Also, our numerical simulations help to constrain the distribution of spatial tectonic stress fields. Furthermore, we infer that the fault core zone in the southwestern Beichuan Fault may have been more severely damaged than the northeastern counterpart, which provides an explanation that the rupture in the northern Beichuan Fault propagates faster than in the southern portion. Besides, we found that the mainshock has increased the Coulomb failure stress on the Wenchuan‐Maoxian Fault (WMF), which did not slip in this event. However, we speculate the mainshock could not significantly push the WMF closer to the edge of a new earthquake. Key Points: Our model with complex multifault geometry and heterogeneous initial stress reproduces major observations of the Wenchuan earthquakeThe rupture speed variations may be caused by the fault damage zones difference, rather than fault geometry and stress heterogeneityThe positive Coulomb stress changes on the Wenchuan‐Maoxian Fault caused by the mainshock may be relaxed by aftershocks on Lixian fault [ABSTRACT FROM AUTHOR]

A novel prefabricated curling rink supported by steel frame and precast concrete blocks has been tested by the 2019 China Youth Curling Open, and that will be responsible for the Beijing Winter Olympics and Winter Paralympics curling competitions in 2022. Due to quite limited researches on the mechanical properties of this professional curling venue, the dynamic behavior of the prefabricated rink under human activities are not well understood. In particular, people and curling stones are potentially more susceptible to the ice vibrations when compared to the traditional curling rink constructed on rammed foundation. Small ice rink vibrations caused by the human locomotion load can make athletes feel uncomfortable, which could affect competition experience, techniques, and skills of the occupancies. At the same time, it can also result in a slightly change of the curling stone trajectories, which ultimately caused the athletes to adopt an erroneous strategy. In order to get a further understanding of the above problems, this paper conducts a series of performance studies based on the 3D finite element model built in ABAQUS and the measured dynamic loads. In this context, it includes the research of on-site measurement of dynamic loads caused by different types of human locomotion on ice sheet, which can provide a reference to the dynamic performance design of prefabricated curling rink supported by similar structural systems. Moreover, the time and amplitude parameters of the footfall forces are extracted to analyze and be compared with the human induced loads results from the existing research, generally obtained on the concrete surface. Then, on the base of the finite element model verified by experiment, the experimental achieved loads are applied for the dynamic analysis to study the vibration acceleration and velocity response of ice sheet. Finally, the vibration response results, including peak acceleration (PA), vibration dose value (VDV), root mean square acceleration (RMS), as well as root mean square velocity were evaluated according to the regulations proposed by the International Olympic Committee and the vibration evaluation standards suggested by AISC design guide, ISO guideline, and VC curves. The analysis results indicate that innovation prefabricated curling ice rink supported by steel-concrete composite floors can meet the requirements of the event and has the prospect of promotion and application. [ABSTRACT FROM AUTHOR]

Electromagnetic forming process is a high velocity forming technique which is widely used in automotive and aerospace sectors for forming and joining metallic sheet/tubes. The geometrical structure of compression coil has significant effect on the performance of the system in terms of current output and deformation of workpiece. The present work aims to analyse the effect of structural parameters of compression coil like cross-section of turns (X), pitch circular diameter (PCD) and effective turn (n) using both experimental and numerical simulation. A bitter compression coil of variable geometrical structure has been considered to see the effect of its parameters by deforming an AA6061 tube experimentally. Parameters like magnetic field, velocity, Lorentz force, displacement and stress are difficult to measure experimentally but have significant indication on performance of the coil in EMF. The trends of numerically predicated parameters find good agreement with experimental deformation value of tube. The FE simulation is carried out to correlate deformation results. The results indicate that n has higher significance in performance of compression coil as compared to X and PCD of coil. [ABSTRACT FROM AUTHOR]

A thorough study of the parameters influencing the operation of devices based on nanowired alumina substrate is presented. The basic structures are realized by growing metallic nanowires inside alumina porous substrate. The control of the areas wherein growth occurs allows building of various microwave devices supported on the filled template. The performances of these devices depend on the material parameters and topology/geometry in presence. These devices have the particularity to combine nanoscale, through the use of nanowires, and millimeter scale that is characteristic of microwave devices and their associated operating wavelength. The gap between the two‐scale ranges implies that analytical models and numerical simulation tools have to be combined to modelize and design performant microwave devices, such as Nanowired Substrate Integrated Waveguides (NSIWs) devices that are the subject of the paper. A deep parametric analysis of the properties and operation of the basic NSIW is presented and is followed by the illustration of two designs: a simple NSIW line, and an EBG NSIW filter. [ABSTRACT FROM AUTHOR]

The accurate modeling of wolfberry plant morphology is the basis for theoretical and simulation analyses of the wolfberry picking process. The curved shape of the fruit branches makes it challenging to model Lycium barbarum (wolfberry) plants. This paper establishes a three-dimensional model of the branches under no gravity through field measurements, and then assesses the morphology of the branches under gravity load, fruit load, and branch load using finite element simulation. An orthogonal rotation combination experiment determined the relationship between branch morphology, length, growth angle, and growth mode parameters. The p-values of the prediction model were 0.0001, 0.0067, and 0.0203, respectively. Finally, the bending shape of the actual branches was verified against the branches generated by the prediction model. The experimental results show that the prediction model accurately models the fruit-bearing branches of Lycium barbarum. This paper introduces a method to quickly predict the bending shape of fruit-bearing branches of Lycium barbarum, providing a theoretical basis for rapid modeling of the L. barbarum plant and a simulation analysis for its harvesting. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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Background: Recently, some adverse effects of moxibustion has been reported such as burns, smoke, allergies, and so on. To overcome the adverse effects of traditional moxibustion, an ultrasonic moxibustion device (UMD) was designed, simulated, fabricated, and tested. The objective of this study is to provide detailed information about the main design parameters, simulation outcome, and performance-test results. Methods: The main components of the UMD are a 1-MHz ultrasonic transducer (UT) with concave lens, and its applicator. The acoustic pressure and temperature distribution of the UT was simulated and described graphically using COMSOL software, which is based on the finite element method (FEM). Experimental verification of the temperature distribution was performed on the skin of pork. The temperature-change profiles of pork in relation to increase of therapy time were obtained at an unfocused point (2 mm) and at a focal distance of 13 mm. For the performance test, moxibustion therapy was conducted on the abdominal skin of mice for 120 min using the new UMD and its histological images were acquired to analyze the skin-tissue damage. Results: The FEM simulation of temperature distribution and acoustic pressure agreed with the experimental outcome. Histological images showed that there was no skin-tissue damage to the mouse abdomens after therapy. The results clearly show that the newly developed UMD can overcome the disadvantages of traditional moxibustion therapy and achieve the proposed design parameters. Conclusion: The FEM simulation and performance tests provided valuable information about developing future UMDs. In addition, its performance can be compared with traditional moxibustion therapy for future study.

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.