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The sample machined with the polygonal path is a common feature in a micro laser-cutting machine. It brings a difficult problem in feedrate planning when the machining accuracy is limited to the scale of sub-micrometer. In this paper, the transition feedrate at the node point is determined by the dynamic capacity of a machine. Then, the jerk-limited feedrate planning is introduced to adjust the feedrate in a smooth manner. The feedrate profile is transferred into the discrete shape for the sampling mechanism of the interpolator in a CNC controller. Moreover, a two-step feedrate planning is proposed to handle the problem that, there exists a distance error, as the line segment is not divisible by the step calculated by feedrate and sample cycle. Firstly, the control parameters, namely, the command feedrate, acceleration and jerk in different stage of the feedrate profile, are estimated by the jerk-limited feedrate planning. Then, a correction scheme is developed to slightly regulate the control parameters. It aims to compensate the distance error caused by the discretization in the process of interpolation. Meanwhile, the proposed method is discussed in two cases according to the length of the line segment. The method of direct adjustment is applied to handle the situation where a line segment is long enough; otherwise, the method of numerical estimation will take the place. Finally, a simulation analysis is presented to demonstrate the performance of the proposed method in feedrate planning. Then, machining experiments are conducted on the self-developed micro laser-cutting machine to verify the effeteness of proposed method. [ABSTRACT FROM AUTHOR]

In production design processes, multiple correlated responses with different distributions are often encountered. The existing literature usually assumes that they follow normal distributions for computational convenience, and then analyzes these responses using traditional parametric methods. A few research papers assume that they follow the same type of distribution, such as the t-distribution, and then use a multivariate joint distribution to deal with the correlation. However, these methods give a poor approximation to the actual problem and may lead to the recommended settings that yield substandard products. In this article, we propose a new method for the robust parameter design that can solve the above problems. Specifically, a semiparametric model is used to estimate the margins, and then a joint distribution function is constructed using a multivariate copula function. Finally, the probability that the responses meet the specifications simultaneously is used to obtain the optimal settings. The advantages of the proposed method lie in the consideration of multiple correlation patterns among responses, the absence of restrictions on the response distributions, and the use of nonparametric smoothing to reduce the risk of model misspecification. The results of the case study and the simulation study validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A new model for mechanical analysis of the main shaft, self-aligning bearing and the cantilever bearingin wellbore trajectory control tool is presented. The theoretical model considered the effects of the parameters of the shell and the main shaft on mechanical analysis. Aiming at the problem of cantilever bearing, a finite element model (FE model) of interaction between cantilever bearing and main shaft is developed. The theoretical model and FE model are verified by experiments. The results show that, the inclination and stress concentration of the needle roller are the main reasons for the failure of the cantilever bearing. The maximum von Mises stress, deformation and inclinationare reduced by 48.62%, 66.19%, 48.09% respectively while changing the fillet radius from 0.25 mm to 0.75 mm. And the stress concentration of the needle roller and the cage in cantileverbearing can also be reduced by changing the distance between the eccentric ring and the bearings, the inner diameter of the shelland others while meeting therequirement of high build-up rate. • Presented a new theoretical model for mechanical analysis of the main shaft • The influence of main shaft parameters was analyzed. • Developed a finite element model to analyze the failure of cantilever bearing • The fillet radius of needle roller have obvious influence on the strength of bearing. • The theoretical model and the FE model were verified by experiments. [ABSTRACT FROM AUTHOR]

This paper analyzes the mechanical characteristics of the hydraulic cylinder rod and the causes of buckling failure. The structural buckling failure often happens to the hydraulic cylinder rod on the flap institutions during the power catwalk operation. The calculation formula of the buckling critical force of the hydraulic cylinder rod is derived by applying the modified boundary conditions. The formula of moment of inertia of different cross sections is deduced, and the calculation formula of the critical force of the hydraulic cylinder rod with defects is obtained by doing research on the rod with the cylindrical defects. Experiments on buckling of hydraulic cylinder rod were conducted on the basis of the simplified test specimen, and the buckling numerical simulation of rod was carried out by using the finite element software Workbench. Through the numerical simulation, we analyze how the radius, depth, and position of the defect to impact the buckling load. The experimental and simulation results show that the formula is accurate when calculating the buckling load of the defect-free hydraulic cylinder rod, and the variation of the buckling load with the cylinder defect parameters was also analyzed. [ABSTRACT FROM AUTHOR]

The plasma brightness cannot be used as a direct indicator of ablation depth detection by femtosecond laser was experimentally demonstrated, which led to the difficulty of depth measurement in the maching process. The tests of microchannel milling on the silicon wafer were carried out in the micromachining center in order to obtain the influences of parameters on the ablation depth. The test results showed that the defocusing distance had no significant impact on ablation depth in LAV effective range. Meanwhile, the reason of this was explained in this paper based on the theoretical analysis and simulation calculation. Then it was proven that the ablation depth mainly depends on laser fluence, step distance and scanning velocity. Finally, a research was further carried out to study the laser parameters which relate with the microchannel ablation depth inside the quartz glass for more efficiency and less cost in processing by femtosecond laser. [ABSTRACT FROM AUTHOR]

The secondary crack is located near the main crack as per the macro examination and micro analysis on the fracture of a PDM (Positive Displacement Motor) shell with special taper thread, and serious defects are produced at the bottom of thread surface in the process of main crack fracture. Scanning electron microscopy observation indicates that the shear fracture point is positioned at shear fracture zone and convex of thread bottom tearing crack of sample 1#. Based on field data and type design of special thread, the matching model of special taper thread of cardan shaft shell is established in this paper, and numerical simulation of threaded connection is carried out under three different borehole curvatures. Results indicate that stress and displacement of thread increase with the borehole curvature. When the curvature reaches 30°/30 m, the maximum Von Mises stress is 967.8 MPa, which is close to the yield stress of thread material. The maximum stress occurs at the bottom of the first tooth according to the actual fracture location. Comprehensive analysis reveals that the effect of bending load occurs many times at the bottom of well. Moreover, thread surface defects result in large stress of thread, and form the weakest micro cracks at the bottom of thread. In addition, the crack occurs in the smooth area, and then rapidly extends to the shear lip, which leads to failure and even fracture of threaded connection of shell. [ABSTRACT FROM AUTHOR]

In this paper, a prediction-correction scheme is proposed to online measure and regulate the milling depth of microchannel using an indicator of laser triggered plasma. Firstly, a prediction model, with respect to the laser fluence and feedrate, is established with several calibration tests using the least square fitting method. It is utilized to change the focal position of objective to track the depth evolution of newly generated surface. Meanwhile, a scanning path for every milling layer with an offset in Z-axis at the beginning and the end of the trajectory, is developed to drive the plasma brightness periodically changing. Then, the milling depth could be obtained when the brightness reaches to the maximum value. By doing so, an online measurement method is presented to estimate the milling depth using the trend of plasma brightness. Furthermore, a correction model is developed to iteratively adjust the feedrate with the online estimated depth. Therefore, the microchannel milling process could be monitored and controlled in a closed-loop manner, in order to accurately regulate the milling depth. Finally, an online measurement and closed-loop microchannel milling is carried out on the self-developed micro-machining center. The effectiveness and correctness of the proposed method are verified by comparing the estimated depth with the actually measured results. [ABSTRACT FROM AUTHOR]

Femtosecond laser micro-drilling has progressed remarkably in recent years to become an essential tool for micro-hole drilling in many applications where the extreme high accuracy machining is required. This paper addresses the problem of finding optimal inspection policy in a femtosecond laser micro-machining process for micro-hole array products to improve successful rate of machined parts and hence to minimise the unit manufacturing cost. A solution algorithm is proposed based on particle swarm optimisation (PSO), and the simulation is used to provide better insight into the optimal solution. The numerical experiments and verification experiments which are conducted with different schemes illustrate the applicability and efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the effect of environmental regulation policy synergy on carbon emissions is essential for the design and decision-making of the other policy combinations. In this paper, the panel data from 30 provinces in China during 2000–2019 are used as samples to investigate the heterogeneity of different policy combinations and compare the differences using a Bayesian non-parametric generalized additive quantile method. The research results imply that the environmental regulation policy synergy has a significant heterogeneous effect on carbon emissions on different levels. Specifically, the effect of environmental regulation policy synergy on carbon emissions has an inverted U-shape trend at the low quintiles, i.e., before the turning point, it shows a "green paradox" effect, and after the turning point, it shows an "emission reduction" effect. However, the effect of environmental regulation policy synergy on carbon emissions shows a significant N-shape trend at the high quintiles, i.e., before the second turning point, it shows an "emission reduction" effect, and after the second turning point, it shows a "green paradox" effect. Moreover, the effect of environmental regulation policy combinations on carbon emissions reduction has been found to vary significantly across regions. • Effect of environmental regulation policy synergy on carbon emissions is explored. • The mediating role of industrial structure is considered. • The effect of ERPS on CE has an inverted U-shape trend at the low quintiles, which shows a significant N-shape trend at the high quintiles. • Significant difference in the efficiency for implementation of ERPS in regions with different levels of CE. [ABSTRACT FROM AUTHOR]

The article at hand focuses on the pressure drop at the hydraulic oscillator valve section. The flow path of the valve section is simplified through the hydraulic oscillator working principle and the valve structure. Further, based on the kinematic model of the positive displacement motor (PDM) and the moving valve, the flow area calculation model between valve sections was deduced. Next, using the simplified valve section flow path, said path is divided into four stages, and the analytical model of pressure drop was established by applying the fluid mechanic theory. Aiming to verify the analytical model, the transient finite element model, and the test bench were set up. Finally, three methods were used to calculate the pressure drop within the 1.3-inch and 1.4-inch stationary valves corresponding to the same input parameters. The results have shown that pressure drops obtained by all the methods are in good agreement; the maximum error between the analytical and experimental results was 7.6 %. Additional comparisons were made between the analytical and finite element model (FEM) results at various flow rates. In that case, the maximum error between the two methods was 7.05 %. Thus, the model can be used to further study the hydraulic oscillator mechanisms and provide a useful reference for both the design and optimization. • By reasonably simplifying the flow channels and pressure drop analytical model of the valve section is established. • Based on the motion relationship between the positive displacement motor and the valve section, the finite element simulation model is established. • The correctness of the theoretical model is verified by comparing with the simulation and experimental data. [ABSTRACT FROM AUTHOR]