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Showing papers in "Journal of Mechanical Science and Technology in 2019"


Journal ArticleDOI
TL;DR: This paper proposes the expert system for accurate fault detection of bearing using advanced signal processing method as wavelet transform and artificial intelligence technique as artificial neural network (ANN) and K-nearest neighbor (KNN), for fault classification of bearing.
Abstract: This paper proposes the expert system for accurate fault detection of bearing. The study is based upon advanced signal processing method as wavelet transform and artificial intelligence technique as artificial neural network (ANN) and K-nearest neighbor (KNN), for fault classification of bearing. An adaptive algorithm based on wavelet transform is used to extract the fault classifying features of the bearing from time domain signal. These features have been used as inputs to proposed ANN models and the same features have also been used for KNN. Dedicated experimental setup was used to perform the test upon the bearing. Single data set for four fault conditions of bearing is collected to train ANN and KNN. The processed and normalized data was trained by using backpropagation multilayer perceptron neural network. The results obtained from ANN are compared with KNN, ANN results proved to be highly effective for classification of multiple faults.

93 citations


Journal ArticleDOI
TL;DR: A new fault diagnosis method that combines three methods, including empirical mode decomposition (EMD), particle swarm optimization support vector machine (PSO-SVM) and fractal box dimension, which can effectively identify gear failure types under different load excitation.
Abstract: Aiming at the problem of gear fault feature extraction and fault classification under different load excitation, we present a new fault diagnosis method that combines three methods, including empirical mode decomposition (EMD), particle swarm optimization support vector machine (PSO-SVM) and fractal box dimension. First, the non-stationary original vibration signal of gear fault is decomposed into several intrinsic mode functions (IMF) by EMD method. Then, the time, frequency, energy characteristic parameters and box dimension are calculated separately from the time domain, frequency domain, energy domain and fractal domain. And then the gear fault characteristics under different load excitation are obtained. Finally, the extracted feature parameters are input into the PSO-SVM model for gear fault classification. The experimental results show that the proposed method can effectively identify gear failure types under different load excitation.

80 citations


Journal ArticleDOI
Qibin Wang1, Bo Zhao1, Hongbo Ma1, Chang Jiantao1, Gang Mao1 
TL;DR: The results show that the proposed two-dimensional deep convolution neural network is good accuracy and fast calculation ability in bearing reliability evaluation and RUL prediction, especially, its time consumption is shorter than that by other deep learning networks.
Abstract: Real-time monitoring and rapid evaluation of bearing operating conditions, especially for the reliability evaluation and remaining useful life (RUL) prediction, are major challenges in the rotating machinery field. A two-dimensional (2-D) deep convolution neural network (CNN) is proposed for rapidly evaluating reliability and predicting RUL, in which a signal conversion method is proposed for converting the one-dimensional signal into the 2-D image to satisfy the input requirements of the 2-D CNN. Different activation functions are employed to implement the conversion of the input data to the output data for each layer of the network, and dropout is only adopted in the hidden layer to change the network structure to prevent overfitting. The maximum correlation entropy with regular terms is employed as the loss function of the model to obtain better training performance compared with the mean square error (MSE). Then, the rolling bearing degradation vibration data is applied to the proposed model to verify the accuracy and rapidity. The results show that the proposed method has good accuracy and fast calculation ability in bearing reliability evaluation and RUL prediction, especially, its time consumption is shorter than that by other deep learning networks.

46 citations


Journal ArticleDOI
TL;DR: In this article, the Schnerr-Sauer cavitation model was adopted to capture the cavitation phase change process and the influence of cavitation on the turbulence intensity was illustrated using the turbulent kinetic energy transport equation, which showed that the pressure diffusion and turbulent transport terms dominate as cavitation occurs.
Abstract: The physical mechanism of flow unsteadiness is one of the key problems in cavitating flow. Significant efforts have been exerted to explain the cavitation-vortex interaction mechanism. As well, the process of kinetic energy transport during the evolution of unsteady cavitating flow must be elucidated. In this work, 2D calculations of cavitating flow around a NACA66 hydrofoil were performed based on the open source software OpenFOAM. The modified shear stress transport k-ω turbulence model, which considers curvature and turbulent eddy viscosity corrections, was employed to close the governing equations. The Schnerr-Sauer cavitation model was adopted to capture the cavitation phase change process. Numerical results showed reasonable consistency with the results of the experiments conducted by Leroux et al. (2004). The results showed that cavitation promotes turbulence intensity and flow unsteadiness around the hydrofoil. During the attached sheet cavity growth stage, high-value regions of turbulent kinetic energy are located substantially at the interface of the cavity, particularly at the rear portion of the cavity region. During the cloud cavity shed-off stage, the cavity begins to break off and the maximum value of turbulent kinetic energy is observed inside the shed cavity. Finally, the influence of cavitation on the turbulence intensity is illustrated using the turbulent kinetic energy transport equation, which shows that the pressure diffusion and turbulent transport terms dominate as cavitation occurs. In addition, cavitation promotes turbulence production and increases dissipation with fluid viscosity and flow unsteadiness. The viscous transport term only acts in the cavitation shedding stage under large-scale vortex shedding. Overall, these findings are of considerable interest in engineering applications.

45 citations


Journal ArticleDOI
TL;DR: In this paper, the flexural behavior of carbon/jute epoxy composites was investigated experimentally and numerically, and the impact response was characterized through drop weight method, which revealed that flexural strength decreases with increase in jute percentage.
Abstract: Natural fiber composites have great potential for reducing the product cost, lowering weight and enhancing renewability. Functionality and performance of natural fibers can be enhanced many folds using them together with synthetic fibers. Hybridization of carbon and low-cost natural jute fiber offers a sustainable hybrid composite having high modulus and mechanical strength. This study investigates flexural behavior of carbon/jute epoxy composites experimentally and numerically. Also, impact response is characterized through drop weight method. Study concludes that flexural strength decreases with increase in jute percentage. Simulation of flexural behavior diverges more than 10 % from experimental results. This anomaly is due to waviness of fiber resulting in heterogeneous property distribution in composites. Further, the fracto-graphic study revealed modes of failure. The drop weight impact tests reveal increased damage area with increase in jute percentage.

44 citations


Journal ArticleDOI
TL;DR: In this article, a case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine blade made of nickel based super alloy IN738LC, which has failed after rendering a useful life of 72000 h.
Abstract: Structure frequency response testing “modal analysis” is an integral part of the development and testing of structures such as pistons, turbine blades, compressor blades, crankshafts, and connecting rods. The usefulness of this technique lies in the fact that the energy in an impulse input is distributed continuously in the frequency domain. Thus, an impulse force will excite all resonances within given frequency range. To detect a fault in the structure, one may require frequency response functions (FRFs) of structures in both conditions, before (healthy structure) and after (failed structure) fault occurs. Now by extracting modal properties from collected FRFs and by comparing modal properties, one can detect and locate the structural faults. A case study is presented in order to detect failure mode and locate cracks on a 30 MW first stage gas turbine blade made of nickel based super alloy IN738LC, which has failed after rendering a useful life of 72000 h. The root causes of failure are detected by comparing the failed blade experimental model with the failed blade computational model. It is observed that the frequencies of the real failed blade experimental model are lesser than the computational model of the failed turbine blade. This is due to the metallurgical defects, which result in loosening of stiffness at the leading and trailing edges of the blade. Further, the stress concentration areas noticed on leading and trailing edges in computational model of the failed blade at the sixth mode are well corroborated with the cracked zone seen on leading and trailing edges of a real case failed turbine blade, collected from the site. It is concluded that the blade has failed due to that the resonance at sixth modal frequency. Scanning electron microscope (SEM) images reveal the presence of corrosion pits on the surfaces of the turbine blade that lead to surface degradation, which results in crack initiation and its propagation with high-cycle fatigue. It is concluded that the failure of turbine blade occurs due to high cycle fatigue.

43 citations


Journal ArticleDOI
TL;DR: In this article, a model of the rotor system with bristle interference is proposed and the nonlinear oil-film force is applied in view of short bearing assumption, and the results indicate that the vibration amplitude of the system with interference is a bit larger than that without interference.
Abstract: To minimize leakage and maintain the efficiency of turbomachinery, brush seal can be installed with zero clearance or interference as the flexibility. This leads to contact between the rotor and bristle pack, and may cause self-excited vibration, even instability. In this study, to establishment a mathematical model of the rotor system, a seal force model with bristle interference is proposed and the nonlinear oil-film force is applied in view of short bearing assumption. The influences of main factors containing rotor rotational speed, installing interval, disc mass, and disk eccentricity on the nonlinear characteristics of the rotor-bearing-brush seal system are conducted by adopting bifurcation diagram, spectrum cascade, axis orbit, and Poincare map. The results indicate that the vibration amplitude of the system with bristle interference is a bit larger than that without interference. The system stability is enhanced with smaller disk mass at a higher rotational speed. The proposed model could provide valuable reference for the design of a rotor-bearing-seal system.

41 citations


Journal ArticleDOI
TL;DR: In this paper, the buckling responses of functionally graded material (FGM) plate subjected to uniform, linear, and non-linear in-plane loads are investigated using trigonometric and exponential function.
Abstract: The paper investigates the buckling responses of functionally graded material (FGM) plate subjected to uniform, linear, and non-linear in-plane loads New nonlinear in-plane load models are proposed based on trigonometric and exponential function Non-dimensional critical buckling loads are evaluated using non-polynomial based higher order shear deformation theory Navier’s method, which assures minimum numerical error, is employed to get an accurate explicit solution The equilibrium conditions are determined utilizing the principle of virtual displacements and material property are graded in the thickness direction using simple Voigt model or exponential law The present formulation is accurate and efficient in analyzing the behavior of thin, thick and moderately thick FGM plate for buckling analysis It is found that with the help of displacement-buckling load curve, critical buckling load can be derived and maximum displacement due to the instability of inplane load can be obtained Also, the randomness in the values of transverse displacement due to inplane load increases as the extent of uniformity of the load on the plate is disturbed Furthermore, the parametric varying studies are performed to analyse the effect of span-to-thickness ratio, volume fraction exponent, aspect ratio, the shape parameter for non-uniform inplane load, and non-dimensional load parameter on the non-dimensional deflections, stresses, and critical buckling load for FGM plates

39 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the internal radial clearance on the damping characteristics, natural modes of vibration, and fatigue life of rolling element bearings was studied, and it was concluded that the dynamic characteristics, and consequently the dynamic performance, of rolling bearings are significantly affected by the internal radii clearance.
Abstract: The performance of rolling element bearings is one of the machine quality measures in industry. The fatigue life and performance of rolling element bearings depends mainly on the dynamic characteristics of those bearings. This paper studied the effect of the internal radial clearance on the damping characteristics, natural modes of vibration, and fatigue life of rolling element bearings. Vibration modal analysis was performed on rolling bearings of the same size and type to measure their dynamic characteristics. These dynamic characteristics include the natural frequency of the first mode of vibration, damping, and amplitude of frequency response function at resonance. The internal radial clearances of these bearings were measured. A statistical analysis was performed to study the correlation between the internal radial clearance and the dynamic characteristics of rolling bearings. It was found that the damping ratio of the bearing assembly increased by reducing the internal radial clearance of the bearing. Similarly, rolling bearings that have large internal clearances showed short predicted fatigue life. It is concluded that the dynamic characteristics, and consequently the dynamic performance, of rolling bearings are significantly affected by the internal radial clearance.

36 citations


Journal ArticleDOI
TL;DR: A deep learning network (DLN) is proposed as the basis for a bearing fault diagnosis technique, which is constructed by the autoencoders and softmax classifier for the purpose of identifying the various multi-degree bearing fault.
Abstract: This paper proposes a deep learning network (DLN) as the basis for a bearing fault diagnosis technique, which is constructed by the autoencoders and softmax classifier for the purpose of identifying the various multi-degree bearing fault. Firstly, the ensemble empirical mode decomposition (EEMD) method is used to decompose the original vibration signal into intrinsic mode functions (IMFs). A high-dimensionality feature vector is formed by analyzing the statistical parameters in the time domain and the frequency domain of the first several IMFs. Then, this feature vector serves as the input for DLN to classify the bearing fault pattern. In a DLN, an autoencoder performs the unsupervised feature self-learning phase to generate a final significant feature vector for training the softmax classifier. Finally, the parameters of a complete DLN based on stacking auto-encoders and the softmax classifier together is fine-tuned with respect to supervised learning criterion aiming to optimize the classification error. Experimental results have shown a great effect for bearing fault diagnosis based on the proposed DLN. The identification accuracy result has been achieved in the bearing fault status even with the unpredictable defects tests on the inner race and roller element of bearing. Methodologies in this study offer confidence for complex data classification.

32 citations


Journal ArticleDOI
Nafiz Yaşar1
TL;DR: In this article, the effects of different feed rate levels and cutting speeds on the surface roughness (Ra) and thrust (Fz) were investigated, and the results showed that there exists an average difference of 4.9 % between experimental and simulation thrust force values, and proved the applicability of the finite element model.
Abstract: AA7075 aluminum alloy attracts scientific interest to participate in production of crucial components in aerospace, construction and automotive domains. Specifically, final products need to display equal quality to ensure the basic standards of safety in the aircraft industry. Despite the high machinability of the AA7075 alloy, hole quality may vary according to tool geometry and drilling parameters. In this study, the effects of different feed rate levels and cutting speeds on the surface roughness (Ra) and thrust (Fz) were investigated. Drilling experiments were conducted with drills of three different quality and geometry. The effects of drilling variables on the surface roughness and the thrust force according to “the smaller-the better” approach of the gray relation analysis (GRA) method have been investigated. Consequently, the highest and lowest gray relations degrees obtained were 0.828 and 0.338, respectively. Numerical analyzes for thrust force were performed with the ThirdWave AdvantEdge simulation software based on the finite element method. We also outlined that there exists an average difference of 4.9 % between the experimental and simulation thrust force values, and we proved the applicability of the finite element model.

Journal ArticleDOI
TL;DR: In this paper, a five degrees-offreedom quasi-static model for angular contact ball bearings (ACBBs) was employed to investigate skidding with ball and race contact forces and inertial loading by rotational speed.
Abstract: Skidding is a phenomenon that frequently occurs in ball–raceway contact areas of bearings and often leads to their early failure. This paper presents a skidding analysis of angular contact ball bearings (ACBBs) subjected to various boundary conditions. A five degrees-offreedom quasi-static model for ACBBs was employed to investigate skidding with ball and race contact forces and inertial loading by rotational speed. The model provided the internal load distribution of all rolling elements, which was subsequently used for the skidding prediction. Hirano’s criterion was used as a theoretical basis for the skidding analysis of ACBBs. Simulations were performed to investigate the influence of external loading, rotational speed, and angular misalignment on the bearing skidding. The effects of the preload method and initial contact angle on the skidding were also considered. As a result, this study provided an in-depth observation of skidding in ACBBs subjected to various operating conditions.

Journal ArticleDOI
TL;DR: In this article, a comparative study was conducted on 3D printed polycarbonate (PC) reinforced acrylonitrile-butadiene-styrene (ABS) composite.
Abstract: 3D printing is one of the most popular additive manufacturing technique due to its usage in vast applications. The process of 3D printed polycarbonate (PC) reinforced acrylonitrile-butadiene-styrene (ABS) composite increases the mechanical properties and yields higher strength for 3D printed structures/products. In this paper, a comparative study was conducted on PC/ABS polymer composites developed using fused deposition modeling (FDM) and conventional compression molding (CM). The proposed study aims at analyzing 3D printed PC/ABS in terms of their processibility, microstructure, and mechanical performance. Three different specimens were prepared with weight percentages (10 wt%, 20 wt%, and 30 wt%) of PC reinforcement in ABS. Mechanical properties of the specimens are used to find the best composition of the composite using FDM and CM. Similarly, the microstructure of specimens is studied to identify the variations in the strength of the polymer composites. This study proves the compatibility of the two polymers. With an increase in the PC content in the sample, the hardness and strength are improved and can provide an excellent amount of strength to the product at a required concentration of PC reinforcement. This phenomenon was explained based on changes in the void formation using micro-structural study. Knowing the appropriate polymer composition, it contributes to printing complex 3D printed with better rational, aesthetic and economic benefits for different applications such as automotive, marine, and several other fields.

Journal ArticleDOI
TL;DR: In this article, a 3D surface contour profilometer was used to measure the surface roughness and observe the morphology of small area; digital optical ultra-depth microscope analysis was carried out to evaluate tool wear and broken; the wear width of the blade was an indicator of the degree of the tool wear; different post milling methods were also compared.
Abstract: Laser additive manufacturing (LAM) technology applied to the 316L stainless steel is attracting interest in the machining industry since it can shorten the production cycle and reduce numbers of machining steps. It still needs to be machined because of the poor surface quality, so the tool wear of post milling process after LAM needs to be studied. However, there are a few studies about the tool wear in milling of laser additive manufacturing stainless steel alloy. The aim of the paper is to evaluate the tool wear performance and surface quality when post milling the 316L stainless steel under different post milling (PM) time. The tool wear behavior was investigated using different analysis techniques. 3-D surface contour profilometer was used to measure the surface roughness and observe the morphology of small area; digital optical ultra-depth microscope analysis was carried out to evaluate tool wear and broken; the wear width of the blade was an indicator of the degree of the tool wear; different post milling methods were also compared. The obtained results demonstrate that the height of the LAM parts were connected with the heat dissipation effect; there are three stages of tool wear: initial wear stage, normal processing stage, and severe broken stage; usually the down-milling is better than up-milling at the bottom surface roughness, quality and edge morphology.

Journal ArticleDOI
TL;DR: In this article, a finite annular prism method (FAPM) was developed for the 3D free vibration analysis of bi-directional functionally graded (FG) annular plates with assorted boundary conditions.
Abstract: Based on Reissner’s mixed variational theorem, the authors develop a finite annular prism method (FAPM) for the three-dimensional (3D) free vibration analysis of bi-directional functionally graded (FG) annular plates with assorted boundary conditions. In this formulation, the FG annular plate is divided into a number of finite annular prisms with triangular cross-sections, in which Fourier functions and Lagrange polynomials are used to interpolate the circumferential direction and radial-thickness surface variations of primary field variables in each individual prism, respectively. The material properties of the FG annular plate are assumed to obey an exponential function distribution varying doubly exponentially through the radial-thickness surface. These FAPM solutions for the frequency parameters and their corresponding mode shapes of the FG annular plate closely agree with the solutions obtained using other 3D approaches available in the literature.

Journal ArticleDOI
TL;DR: In this paper, a polishing path programming method of the elastic grinding tool was studied, and feed mode and parametric method for the blade profile were proposed, and calculation methods of offset surface, polishing spacing and step size and cutter-axis vector were given; the polishing test results indicate that after polishing, blade surface roughness is smaller than 04 μm and blade profile tolerance is within the tolerance zone.
Abstract: As for blisk blade profile polishing, the “five-axis numerical control + flexible grinding head + elastic grinding tool” polishing process equipment has advantages of high precision, little interference, good adaptivity, etc; in order that the elastic grinding tool (abrasive cloth wheel) can effectively fit in with the blade profile in the polishing process and polishing quality and efficiency can be improved, a polishing path programming method of the elastic grinding tool was studied, feed mode of the elastic grinding tool and parametric method of the blade profile were proposed, and calculation methods of offset surface, polishing spacing, polishing step size and cutter-axis vector were given; this polishing path programming method makes it possible for the flexible spindle mechanism keeps a reasonable pose during the polishing process so that the elastic grinding tool can not only effectively fit in with the blade profile but also the polishing force direction of the elastic grinding tool is basically identical with normal vector direction of the polishing point; the polishing test results indicate that: After polishing, blade surface roughness is smaller than 04 μm and blade profile tolerance is within the tolerance zone, thus satisfying technical requirements and indicating that the technology proposed in this paper can satisfy blisk blade profile polishing requirements

Journal ArticleDOI
TL;DR: The improved TSBP method is introduced, which not only provides an accurate and precise point prediction of RUL but also specifies the confidence interval of Rul prediction, which can enhance the T SBP method for uncertainty management.
Abstract: Trajectory similarity-based prediction (TSBP) is an emerging real-time remaining useful life (RUL) prediction method that has drawn considerable attention in the field of data-driven prognostics. TSBP is fast, and the corresponding model is easy to train. However, TBSP only provides a point estimation of RUL, which is insufficient for some specific prognostic applications. Hence, this study introduces an improved TSBP method to handle the issue of prognostic uncertainty. On the basis of an adaptive kernel density estimation technique and β-criterion, the improved TSBP method not only provides an accurate and precise point prediction of RUL but also specifies the confidence interval of RUL prediction. The capability of obtaining the confidence interval of RUL can enhance the TSBP method for uncertainty management. The effectiveness of the proposed method is validated through two cases studies, which are related to turbofan engine prognostics.

Journal ArticleDOI
TL;DR: In this paper, the entropy generation analysis for a carbon nanotube (CNT) suspended nanofluid flow by a wedge with thermal radiation and convective boundary condition was performed.
Abstract: We performed entropy generation analysis for a carbon nanotube (CNT) suspended nanofluid flow by a wedge with thermal radiation and convective boundary condition. The multi-wall carbon nanotube (MWCNT) with water as the base fluid was considered. Two-dimensional governing equations were transformed by similarity method into a set of coupled nonlinear ODEs and then solved analytically using optimal homotopy asymptotic method (OHAM). Moreover, solutions of these equations were further utilized in a dimensionless equation of entropy generation. The analytical results indicated that the entropy generation can be reduced by increasing radiation parameter and reducing the convection through boundaries, while nanoparticles have influence to increase the entropy production.

Journal ArticleDOI
TL;DR: The experimental results show that the VMD-Hilbert envelope spectrum can better reflect the fault characteristics than the time domain spectrum, and the proposed fault diagnosis method under variable load has higher recognition accuracy than other comparison methods.
Abstract: The working conditions of rolling bearings during the running change in real time. Aiming at the problem of fault diagnosis of rolling bearing under complex working conditions, a new fault diagnosis (VHDBN) method based on variation mode decomposition (VMD), Hilbert transform (HT) and deep belief network (DBN) is proposed in this paper. Firstly, the proposed fault diagnosis method performs the VMD decomposition for the time domain signal in order to obtain a series of intrinsic mode functions (IMFs), and Hilbert envelope spectrum is obtained by Hilbert transform. The Hilbert envelope spectrum is used to construct the feature matrix, which is used as an input of the DBN network in order to obtain a fault diagnosis model. In order to test and verify the effectiveness of the proposed fault diagnosis method, the experimental data of rolling bearings under variable load is used in here. The experimental results show that the VMD-Hilbert envelope spectrum can better reflect the fault characteristics than the time domain spectrum, and the proposed fault diagnosis method under variable load has higher recognition accuracy than other comparison methods.

Journal ArticleDOI
TL;DR: An artificial neural network was adopted in the construction of an accurate nonlinear function between the optimization objective and the design variables of impellers to increase efficiency at the design point of a centrifugal pump.
Abstract: To increase efficiency at the design point of a centrifugal pump, this study adopted an artificial neural network in the construction of an accurate nonlinear function between the optimization objective and the design variables of impellers. Modified particle swarm optimization was further applied to refine the mathematical model globally. The database, which consisted of 200 sets of impellers, were generated from the Latin hypercube sampling method, and their corresponding efficiencies were obtained automatically from numerical simulation. Design variables were the distributions of blade angles, and results established that the difference between the numerical performance curve and the experimental results was acceptable. Optimization with a two-layer feedforward network improved the pump efficiency at the design point by 0.454 %. Flow complexity improved as the blade curvature increased. The application of the multilayer neural network could provide a meaningful reference to single- and multi-objective optimization of complex and nonlinear pump performance.

Journal ArticleDOI
TL;DR: In this article, the effect of Coulomb friction on a quasi-zero stiffness (QZS) isolator which configured by combining an Euler buckled beam negative stiffness corrector and a linear isolator is presented.
Abstract: The effect of the Coulomb friction on a quasi-zero stiffness (QZS) isolator which configured by combining an Euler buckled beam negative stiffness corrector and a linear isolator is presented in this paper. Assuming friction damping provided by linear roller guider, the dynamic responses of the vibration isolation system and the equivalent linear one are obtained by using harmonic balance method (HBM). The static and dynamic characteristics of the QZS isolator are both investigated. For the linear isolator, the resonance frequency will increase and the peak transmissibility will decrease with the increasing of Coulomb friction or the decreasing of the excitation amplitude. However, in the case of QZS isolator, the natural frequency is decreased with the help of the negative stiffness mechanism and the amplification factor at the resonance is not obvious with the presence of the friction damping. Theory and experiment show good accordance. Therefore, it is recommend that one should add light Coulomb friction damping into the system to get better performance when using the QZS isolator in practice. The results present here can be a useful guideline when design such kind of vibration isolator.

Journal ArticleDOI
TL;DR: A rollover crashworthiness analysis and optimization method of bus frame using the RTWBs and DRTWBs is presented, which verifies that the frame model can obtain high roll over crashworthiness and lightweight bus structure.
Abstract: At the conceptual design stage, utilizing the detailed model to determine the rollover crashworthiness of bus structure would need long design cycle. Currently, rectangular thin-walled beams (RTWBs) are extensively used to create the real bus because of the excellent manufacturability. Remarkably, dual rectangular thin-walled beams (DRTWBs) can generate higher bending resistance. Therefore, this paper presents a rollover crashworthiness analysis and optimization method of bus frame using the RTWBs and DRTWBs. The bus frame with tire, suspension and platform structures is created in the CarFrame software. Analysis numerical example verifies that the frame model, which reduces the modeling and computational costs, is in excellent agreements with the detailed model, and optimization numerical example verifies that the frame model can obtain high rollover crashworthiness and lightweight bus structure. Therefore, the frame model can effectively replace the detailed model for the rollover crashworthiness analysis and optimization.

Journal ArticleDOI
TL;DR: In this paper, the effects of welding parameters on joint quality and microstructure of low carbon steels were characterized by microstructural and mechanical properties using tungsten alloy tool.
Abstract: Low carbon steels could be simply welded by conventional fusion welding processes. However, fusion joining of these steels results to the problems related to melting of metal and solidification of weld pool. In the present study, friction stir welding (FSW) of low carbon steel plates was undertaken using tungsten alloy tool to determine the effects of welding parameters on joint quality. Welded joints were characterized by microstructural and mechanical properties. Onion rings, banded structure and swirl zone were observed as a result of process temperature, strain rate, plastic deformation, and material transportation. The results indicate that the grain size of the weld zone is different from the base metal (BM) and slightly lesser to the base metal in the middle region of stir zone. Comparing the advancing side (AS) and retreating side, grain size was similar in the heat affected zone and different in the thermo-mechanically affected zone. The microstructure provides the suitable relationship for the properties and micro hardness of the welded region. Tungsten carbides rich areas were found in the stir zone performed at high heat input weld condition. Interestingly, there is noticeable change in grain size and grain distribution of the tungsten tool after welding.

Journal ArticleDOI
TL;DR: In this paper, the influence of cutting parameters and coating materials on the machined surface roughness was studied and the smallest resultant cutting force was obtained by TiN/TiCN/TiAlN multicoated tool.
Abstract: The TiAlN+TiN coated tool, AlTiN coated tool and TiN/TiCN/TiAlN multi-coated tool were chosen for the high-speed milling of AISI 4340. The resultant cutting force and tool wear of coated tools were reviewed. The influence of cutting parameters and coating materials on the machined surface roughness was studied. The smallest resultant cutting force was obtained by TiN/TiCN/TiAlN multicoated tool. The main wear mechanisms of coated tool were chipping, collapse, the chipping of coating, adhesive wear, abrasive wear and crater wear. The minimal flank wear width was obtained by TiN/TiCN/TiAlN multi-coated tool. Among the selected cutting parameters, the lower surface roughness Ra of 0.08≈0.32 μm was achieved by the TiN/TiCN/TiAlN multi-coated tool and TiAlN+TiN coated tool. This work was conducive to the selection of coated tools and the optimization of cutting parameters in high-speed milling of AISI 4340, as well as to the promotion of high-efficiency and high-quality machining of hard-to-cut material.

Journal ArticleDOI
TL;DR: In this paper, the impacts of reinforced Al6061 composite with 5 wt% of Fe2O3 in addition to 2 %, 4 %, 6 % weight of B4C being made-up by stir casting technique are investigated.
Abstract: The modifications of Al6061-T6 metal matrix composites is an extraordinary enthusiasm of recent pertinence for lesser weight materials with high value of tensile strength, hardness and wear protection, which can be widely used in automotive and aircraft design. In this paper, we investigate the impacts of the reinforced Al6061 composite with 5 wt% of Fe2O3 in addition to 2 %, 4 %, 6 % weight of B4C being made-up by stir casting technique. In this research, Al6061 composites have analyzed by its physical and mechanical properties like as density, hardness, impact strength, ultimate tensile and compressive strength, and an optical microscope is utilized to assess the metallurgical properties such as microstructure with different wt% of reinforcement of Al6061 composite. The microstructure of newly prepared composites was shown a regular spreading of reinforcements in the matrix by an optical microscope and also the muscular bonding between the matrix and reinforcements were demonstrated by SEM analysis. It is further identifying that, microstructure uniformity and therefore the tensile strength of the metal composites was enhanced with increasing the fraction of Fe2O3 and B4C particles without any decrement in elongation.

Journal ArticleDOI
TL;DR: In this article, a centrifugal pump with a specific speed of 39.12 m×min-1×m3s-1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test.
Abstract: In this study, a centrifugal pump with a specific speed of 39.12 m×min-1×m3s-1 is treated to analyze the flow instability under part-load conditions by numerical simulation and experimental test. For calculations, the RANS method, coupled with the k-ω SST turbulence model, is adopted. Numerical results at different operation points are compared with available experimental data, such as hydraulic performance and flow field information by particle image velocimetry. The numerical and experiment results agree well. The flow simulation indicates a strong reverse flow at the passage upstream impeller inlet, and the energy loss in the impeller is the largest under part-load conditions among all flow components in the pump. In one impeller revolution, one blade-to-blade flow passage is always nearly blocked off by the rotating stall occurring at the impeller inlet for each instant, and the blockage induces a jet flow with large velocity at the next blade-to-blade flow passage along the rotational direction of the impeller. The blockage and the jet flow in the blade-to-blade flow passages will make the flow unstable inside the impeller and cause performance breakdown and pressure vibration under part-load conditions for the pump.

Journal ArticleDOI
TL;DR: Big data on customers’ experience with front loading washers, represented by reviews and ratings on the BestBuy website, were collected and used to analyze the relationship between the customers' experience and the associated satisfaction by using text analytics, showing that the quantitatively elicited customer information from the big data can provide insights for new washing machine design.
Abstract: The volume of online consumer-generated content, such as opinions, personal feelings, and design requirements continually increases. However, the analysis of the large quantity of data available is not systematic, and customers’ opinions and requirements are not properly utilized in product design. In this study, big data on customers’ experience with front loading washers, represented by reviews and ratings on the BestBuy website, were collected and used to analyze the relationship between the customers’ experience and the associated satisfaction by using text analytics. Words related to customer satisfaction that occurred frequently in the reviews were extracted, and the most significant words among them were selected as inputs for finding the major factors relevant to washer design by performing factor analysis. The influence of each factor was quantitatively estimated through linear regression analysis. This shows that the quantitatively elicited customer information from the big data can provide insights for new washing machine design.

Journal ArticleDOI
TL;DR: In this paper, in-situ synthesized nanocomposites of poly (methyl methacrylate) (PMMA) and TiO2 for use as dental materials are presented.
Abstract: This paper presents the application of the in-situ synthesized nanocomposites of poly (methyl methacrylate) (PMMA) and TiO2 for use as dental materials. TiO2 nanoparticles with different percentages (1wt% and 2 wt%) were blended with PMMA through a melt compounding process. The prepared nanocomposites were characterized by a micro-indentation test, scratch test, and field emission scanning electron microscopy analysis. The effects of different vol. % of TiO2 on the mechanical properties of the composites were studied. The evaluation of the mechanical properties of the composites revealed that the utilization of TiO2 as a reinforcing agent strengthened the polymer. The morphological observation demonstrated the presence of significant adhesion between TiO2 and the polymer matrixes with a homogeneous distribution of TiO2 in the polymer matrix. The proper compatibilization between TiO2 and the polymer matrix enhanced the mechanical properties. Overall, this work may pave the way for the production of a new compatibilized TiO2-based blend for dental applications.

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Min Zou1, Pan Fang1, Huan Peng1, Hou Duyu1, Mingjun Du1, Yongjun Hou1 
TL;DR: The research result shows that the synchronous ability between the two unbalanced rotors actuated by dual-frequency excitation is related to the distance from the rotating center of the motor to the centroid of supporting body, and the greater the distance value, the better the synchronization of the vibrating system.
Abstract: In petroleum drilling engineering, drilling shakers are critical devices for cleansing solid particles and recycling drilling fluid. For the problem that the vibration screen with a single frequency usually results in flurry overflow due to the blocking of screen mesh, a selfsynchronous vibratory system with dual-frequency and dual-motor excitation is proposed. But it is not clear about the synchronization mechanism and dynamic characteristics of the system, which causes a lack of theoretical description for the source of synchronization phenomenon. Hence, this paper explores the synchronization mechanism and dynamic characteristics around the proposed system above. First, vibration and stability theory are employed to master the dynamic characteristics of the system, and the dynamic model is established by Lagrange equation. Then, displacement responses of the system are obtained by dimensionless formulas. Synchronous condition and synchronous stability between the unbalanced rotors are derived with small parameter method and Poincare method. Finally, some computer simulations are implemented to further verify the correctness of the theoretical analysis. The research result shows that the synchronous ability between the two unbalanced rotors actuated by dual-frequency excitation is related to the distance from the rotating center of the motor to the centroid of supporting body, and the greater the distance value, the better the synchronization of the vibrating system. This study will promote the recycle technology development of drilling fluid and settlement of the common scientific issues in vibrating synchronization.

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TL;DR: In this article, a CVD Al2O3/TiCN coated carbide tool was used for high-speed dry milling of AISI 4340 steel and the relationship between cutting force, surface roughness and cutting parameter was investigated.
Abstract: The high-speed dry milling of AISI 4340 steel was carried out with a CVD Al2O3/TiCN coated carbide tool. The relationships between cutting force, surface roughness and cutting parameter were conducted, and the influence of tool wear on cutting force and surface roughness was also investigated. The wear mechanism of coated tool was revealed by SEM micrograph and EDS analysis. Due to the lower tool wear rate, the increase of cutting forces and surface roughness Ra was smaller at the initial wear stage and the steady wear stage, whereas the increase of cutting forces was improved suddenly when the flank wear was more than 0.25 mm. Additionally, the coated tool wear was mainly caused by adhesion, abrasion, oxidation and diffusion, accompanied with a little peeling and chipping. The research results are expected to provide optimum cutting parameters for high-efficiency machining of high-strength steel.