Explore the vast range of titles available.

Rail weld irregularities are one of the primary excitation sources for vehicle-track interaction dynamics in modern high-speed railways. They can cause significant wheel-rail dynamic interactions, leading to wheel-rail noise, component damage, and deterioration. Few researchers have employed the vehicle-track interaction dynamic model to study the dynamic interactions between wheel and rail induced by rail weld geometry irregularities. However, the cosine wave model used to simulate rail weld irregularities mainly focuses on the maximum value and neglects the geometric shape. In this study, novel theoretical models were developed for three categories of rail weld irregularities, based on measurements of the high-speed railway from Beijing to Shanghai. The vertical dynamic forces in the time and frequency domains were compared under different running speeds. These forces generated by the rail weld irregularities that were measured and modeled, respectively, were compared to validate the accuracy of the proposed model. Finally, based on the numerical study, the impact force due to rail weld irrregularity is modeled using an Artificial Neural Network (ANN), and the optimum combination of parameters for this model is found. The results showed that the proposed model provided a more accurate wheel/rail dynamic evaluation caused by rail weld irregularities than that established in the literature. The ANN model used in this paper can effectively predict the impact force due to rail weld irrregularity while reducing the computation time.

Wheel polygon amplitude can greatly affect wheel-rail vibration and sound radiation. Based on multi-body dynamics theory, a vehicle-track rigid-flexible coupling dynamics model was established. According to the actual running wear condition of the wheel, the wheel-rail vibration response was calculated and analyzed (the order of wheel polygons is 20, and the polygon amplitude is 0.01/0.02/0.03/0.04 mm, respectively). Together with the finite element/boundary model of the wheel, the calculated wheel-rail force was used as an external incentive to analyze the effects of polygon amplitude on the time-frequency domain of wheel noise. The research results show that: when the polygon order is 20, with the increase of polygon amplitude, the wheel-rail vertical force and the acceleration of wheel, rail and track slab increase gradually. It’s also found that the rail acceleration is obviously more sensitive to the amplitude than the track slab acceleration, while the vertical displacement of the rail and track slab is less sensitive to the polygon amplitude. At the same amplitude, the closer to the wheel rolling line, the more obvious the sound pressure decreases with the increase of height. At different amplitudes, the sound pressure at different positions will increase with the rise of the polygon amplitude. The root mean square value of sound power increases gradually with the addition of amplitude: When the amplitude changes from 0.01 mm to 0.04 mm, the calculated sound power increases by 4.1 dB.

This study aimed to examine how downward loads influence the torque/force and shaping outcome of ProTaper NEXT (PTN) rotary instrumentation. PTN X1, X2, and X3 were used to prepare J-shaped resin canals employing a load-controlled automated instrumentation and torque/force measuring device. Depending on the torque values, the handpiece was programmed to move as follows: up and down; downward at a preset downward load of 1 N, 2 N or 3 N (Group 1N, 2N, and 3N, respectively; each n = 10); or upward. The torque/force values and instrumentation time were recorded, and the canal centering ratio was calculated. The results were analyzed using a two-way or one-way analysis of variance and the Tukey test (α = 0.05). At the apex level, Group 3N exhibited the least canal deviation among the three groups (p < 0.05). The downward force was Group 3N > Group 2N > Group 1N (p < 0.05). The upward force, representing the screw-in force, was Group 3N > Group 1N (p < 0.05). The total instrumentation time was Group 1N > Group 3N (p < 0.05). In conclusion, increasing the downward load during PTN rotary instrumentation improved the canal centering ability, reduced the instrumentation time, and increased the upward force.

The machining of thin-walled elements used in the aviation industry causes may problems, which create a need for studying ways in which undesirable phenomena can be prevented. This paper presents the results of a study investigating face milling thin-walled elements made of titanium alloy, aluminum alloy and polymer composite. These materials were milled with folding double-edge cutters with diamond inserts. The results of maximum vertical forces and surface roughness obtained after machining elements of different thicknesses and unsupported element lengths are presented. The results of deformation of milled elements are also presented. The results are then analyzed by ANOVA. It is shown that the maximum vertical forces decrease (in range 42–60%) while the ratio of vertical force amplitude to its average value increases (in range 55–65%) with decreasing element thickness and increasing unsupported element length. It is also demonstrated that surface roughness deteriorates (in range 100% for aluminum, 30% titanium alloy, 15% for CFRP) with small element thicknesses and long unsupported element lengths. Long unsupported element lengths also negatively (increasing deformation several times) affect the accuracy of machined elements.

In practice, the assessment and treatment of rail corrugation are quantitatively based on the corrugation depth. Wheel–rail vertical forces (WRVF), as a direct reflection of wheel–rail interaction, can give expression to the corrugation depth and thus serve as a key parameter for assessing the corrugation. In this paper, we propose an evaluation method for rail corrugation based on the WRVF. First, a 3D wheel–rail dynamic finite element (FE) model was developed with typical parameters of CRTS II slab track and CRH3 vehicle for high-speed railways in China. The accuracy of the model was then validated with the measured WRVF data in the field. Second, using the validated model, the time–frequency domain distribution of WRVF (vehicle speed: 300 km/h) was obtained with consideration of the corrugation wavelength in the range of 40–180 mm. The non-linear least squares method and rational equation were used to fit the function between the large value of WRVF and the corrugation depth value under the conditions of different corrugation wavelengths. Next, effects of the Pinned–Pinned resonance frequency and vibration mode on the fitted parameters were analysed, by which an indicator for corrugation treatment (grinding) was proposed. Finally, the indicator was applied in the monitoring of rail corrugation for high-speed railway lines in the field. The results show that the misjudgement rate of rail grinding decisions (using the proposed indicator) is low with the accuracy at 92.5%. The proposed method can provide a basis for the rail corrugation evaluation and grinding decisions-making.

The vertical tire force can be utilized to obtain information on the longitudinal and lateral force of the tire through the tire friction circle. This means that ride safety can be improved by using the longitudinal force that affects the vehicle’s driving performance and the lateral force that allows for stable cornering without slips. In this paper, we propose a vertical tire force estimation method using sensors that can be implemented in the vehicle. First, the issue of the observability of the tire force is investigated, then we introduce a tire force observer that utilizes the acceleration of the sprung and the displacement between the sprung and unsprung mass. In the proposed observer design, the change in the road surface is taken into consideration as a Gaussian random variable. In addition, a 1/5 scaled quarter car model is developed as an experimental apparatus to evaluate the proposed method, and the proposed method is validated through simulation and experiment.

The effect of process parameters on vertical forces and temperatures developed during friction stir welding of AZ31 magnesium alloy sheets was widely investigated. To this end, friction stir welding (FSW) experiments were carried out with constant values of the rotational and welding speeds in the ranges from 1200 to 2500 rpm and from 30 to 100 mm/min, respectively. The influence of the time between the end of the sinking stage and the beginning of the welding one was also studied using dwelling time values ranging from 0 to 120 s. Vertical forces occurring during all stages of FSW were measured using a low-cost dynamometer developed by authors. Furthermore, temperatures in different positions of the welding line were monitored by means of K-type thermocouples. It was shown that during the dwelling stage, the vertical force decreases until a steady-state regime is reached. However, the dwelling time does not significantly affect the force value in the welding stage. The vertical force versus time curve promptly reaches a steady state during the welding stage. The force value rises with increasing welding speed and decreasing rotational speed; such effect is consistent with the one showed by rotational and welding speeds on temperature measured in different positions during FSW. Finally, forces and temperatures have been related to the mechanical properties of the joints. It was shown that both the ultimate tensile strength and ultimate elongation exhibit the highest values under the process parameters leading to the lowest vertical force and highest welding temperature.

In the present study, the tool shoulder end features such as concentric circle shoulder tool (T CC ), ridge shoulder tool (T R ), knurling shoulder tool (T K ), and scroll shoulder tool (T S ) were designed, and their effect on weld size, vertical force, temperature distribution, and material flow was investigated during friction stir welding (FSW) of Al-Mg-Si alloy. The vertical force, tool torque, and temperature during the welds were measured and compared for all the tools. The deformed marker material was used to analyze the material flow caused by the shoulder and pin. The experimental results show that the welds with shoulder end featured tools of smaller shoulder diameter ( ϕ 18 mm )were comparable with the welds with plane shoulder tool (T P ) of larger shoulder diameter ( ϕ 21 mm ) in the aspects of temperature and weld strength with reduced weld size. At initial stage, the plasticized material, beneath the tool shoulder, moves from advancing side (AS) to retreating side (RS) whereas the material around the pin moves from RS to AS. Overall, the welds produced with the proposed tool shoulder end features achieved lower vertical force, higher temperature, and minimum/no flash compared to T P of equal/higher shoulder diameter. The welds produced with T R resulted in better mechanical properties with lower vertical force, i.e., approximately 36% than that of (T P ) 21 tool and the hardness of weld zone is at a value of 65–78 HV 0.1 .

A multivariable empirical model based on an artificial neural network (ANN) was developed in order to predict the vertical force occurring during friction stir welding (FSW) of sheets in AZ31 magnesium alloy. To this purpose, FSW experiments were performed at different values of rotational and welding speeds, and the vertical force versus time curve was recorded during the different stages of the process by means of a dedicated sandwich dynamometer. Such results were used in the training stage of the artificial neural network-based model developed to predict vertical force versus time curves. A multi-layer feed forward ANN, using the back-propagation algorithm, consisting of the input layer with four input parameters (rotational speed, welding speed, rotational speed to welding speed ratio and processing time), two hidden layers with four neurons each, and the output layer with the vertical force as output, was built and trained. The generalization capability of the ANN was tested using a two-step procedure: in the former, the leave-one-out cross-validation method was used whilst, in the latter, curves not included in the training dataset were taken into account. The low values of the relative error and average absolute relative error, and the high correlation coefficients between predicted and experimental results have proven the excellent capability of the artificial neural network in modeling complex shape of the curve and in capturing the effect of the process parameters on the vertical force without a priori knowledge of the complex microstructural and mechanical mechanisms taking place during friction stir welding. Finally, the relationship between vertical force and processing time, at different welding and rotational speeds, was also predicted using the support vector machine algorithm and the results were compared with those given by the ANN-based model.

In this paper, the propagation of surface gravity waves over multiple bottom-standing porous semicircular humps is examined in the absence and presence of double floating C-type detached asymmetric breakwaters. Both wave scattering and trapping phenomena are investigated within the framework of small-amplitude linear water wave theory, with the governing problem numerically solved using the multi-domain Boundary Element Method (BEM) in finite-depth water. A detailed parametric analysis is conducted to evaluate the effects of key physical parameters, including hump radius, porosity, spacing between adjacent humps, and the separation between the two C-type detached breakwaters. The study presents results for reflection and transmission coefficients, free-surface elevations, and the horizontal and vertical forces acting on the first perforated semicircular hump, as well as on the shore-fixed wall. The findings highlight the significant role of porous humps in altering Bragg scattering characteristics. For larger wavenumbers, wave reflection increases notably in the presence of a vertical shore-fixed wall, while it tends to vanish in its absence. Reflection is also observed to decrease with an increase in semicircle radius. Furthermore, as the wavenumber approaches zero, the vertical force on multiple permeable semicircles converges to zero, whereas for impermeable semicircles, it approaches unity. In addition, the horizontal force acting on the shore-fixed wall diminishes rapidly with increasing porosity of the semicircular humps.