The localized faults of rolling bearings can be diagnosed by the extraction of the impulsive feature. However, the approximately periodic impulses may be submerged in strong interferences generated by other components and the background noise. To address this issue, this paper explores a new impulsive feature extraction method based on the sparse representation. According to the vibration model of an impulse generated by the bearing fault, a novel impulsive wavelet is constructed, which satisfies the admissibility condition. As a result, this family of model-based impulsive wavelets can form a Parseval frame. With the model-based impulsive wavelet basis and Fourier basis, a convex optimization problem is formulated to extract the repetitive impulses. Based on the splitting idea, an iterative thresholding shrinkage algorithm is proposed to solve this problem, and it has a fast convergence rate. Via the simulated signal and real vibration signals with bearing fault information, the performance of the proposed approach for repetitive impulsive feature extraction is validated and compared with the noted spectral kurtosis method, the optimized spectral kurtosis method based on simulated annealing, and the resonance-based signal decomposition method. The results demonstrate its advantage and superiority in weak repetitive transient feature extraction.

A New Family of Model-Based Impulsive Wavelets and Their Sparse Representation for Rolling Bearing Fault Diagnosis

Artificial intelligence systems for tool condition monitoring in machining: analysis and critical review

Benefits for your Students • Access to ASME student competitions/E-Fests, scholarships, internships and more • Exposure to the engineering community and real world situations, in and out of the classroom • Technical information & interactive tools to help with coursework and research • Mentoring by an experienced professional • Networking in person & online, locally & worldwide • Valuable relationships that can last a lifetime • Easy application process with no additional costs Benefits for your School • Supplements your curriculum and coursework • Provides targeted and relevant experiences beyond the classroom • Keeps you connected to the latest trends and industry developments • Offers exposure to international issues & perspectives • Exemplifies your exceptional commitment to your program and your students • Easy program administration, and the convenience of making a single payment

American Society of Mechanical Engineers (ASME)

This paper presents a new S trajectory kinematic measurement method to evaluate the dynamic accuracy of five-axis machine tools based on R-test measurements. The S trajectory is obtained by scaling the machining path of the S-shaped test piece to the measuring stroke of the R-test. A geometric and dynamic accuracy simulation model is established to analyze the influence of various error factors on the S trajectory test and compare with the conical kinematic test described in ISO10791.6 quantitatively. The simulation results shown that the S trajectory test is more sensitive to most geometric errors and dynamic errors than the conical test. Particularly, to reflect the dynamic error factors such as poor rigidity of machine tools, servo mismatch, reverse error and nonlinear error, the S trajectory test has obvious advantages. Meanwhile, compared with the actual S-shaped piece machining, which is under development for inclusion in ISO 10791.7, the proposed non-cutting kinematic test method can simply reflect the dynamic accuracy of five axis machine tools itself without the interference of other factors and does not require additional workpiece and testing equipment. The proposed method is verified through experiments on a five-axis machine tool.

Dynamic accuracy evaluation for five-axis machine tools using S trajectory deviation based on R-test measurement

The modelling of volumetric errors of machine tools has been widely used by the method of Homogeneous Transformation Matrix (HTM) based on rigid body kinematics analysis for a long time. Without spindle induced errors and thermal errors, to establish a closed-loop HTM for a three-axis machine tool, the total of 21 geometric errors are the primary elements to be known. It is well known that the measured points of translational errors are directly related to the volumetric error at the tool cutting point through rigid body kinematics. In the generalized HTM method, however, this relationship is missing. This report, therefore, proposes a new comprehensive approach to formulate the volumetric errors based on the famous Abbe principle in order to derive the error term in the motion direction, and Bryan principle to derive the error terms in orthogonal to the motion direction. The proposed methodology is simple in concept, rational in physical meaning and easy in implementation. Experimental results, including faster multi-degree-of-freedom error measurements, volumetric error analysis and compensation on a testbed of small machine tool, validate the correctness and effectiveness of this method.

A novel modeling of volumetric errors of three-axis machine tools based on Abbe and Bryan principles

The olivine LiFePO4/C composite cathode materials for lithium-ion batteries were synthesized by solid state reduction method using mixed iron sources. The effects of different temperatures on the electrochemical performance of as-synthesized cathode materials were investigated and analyzed. The crystal structures and the electrochemical performances were characterized by SEM, galvanostatical charge-discharge testing and AC-impedance, respectively. The results demonstrated that the LiFePO4/C composite cathode material synthesized at 710°C and with 1/2(FeC2O4·2H2O/Fe2O3) molar ratio of mixed iron sources has the better electrochemical performance, it has a discharge capacity of 126.1mAh/g at 0.2C and the capacity is kept at 113.8mAh/g after 20 cycles.

Synthesis of LiFePO4/C Composite Cathode Materials by Solid State Method Using Mixed Iron Sources

As an important nonlinear optical material, potassium dihydrogen phosphate (KDP) crystal is used in high-power laser beams as the core element of inertial confinement fusion. It is the most general method of single point diamond fly-cutting (SPDF) to produce high precision and crack-free KDP surfaces. Nevertheless, the cutting mechanism of such material remains unclear, and therefore needs further analysis. Firstly, the stress field, cutting force and cutting temperature under different working conditions are calculated by a KDP crystal cutting simulation model. Then, the rules and the cause of change and interaction mechanisms of force and temperature are analyzed by comparing the measurement experiments with simulations. Furthermore, the causes of chip formation and micro-cracks on the machined surface are analyzed based on thermo-mechanical coupling and chip morphology. The conclusion can be deduced: Although the temperature has not reached the phase transition temperature during the finishing process, under high cutting speeds and large unformed chip thickness, such as semi-finishing and roughing, the temperature can reach up to 180 °C or higher, and KDP crystals are very likely to phase transition-chip morphology also verifies this phenomenon.

https://www.mdpi.com/2072-666X/12/8/855/pdf

Interaction Mechanism of Thermal and Mechanical Field in KDP Fly-Cutting Process

LiFePO4/C(LFP/C) composite cathode material was synthesized by carbon thermal reduction route with the sucrose as reducing agent and characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Some parameters were optimized by means of determining the amount of sucrose and Li2CO3. The electrochemical performances were also tested through assembling batteries. The experimental results demonstrated that the proper theoretic coated carbon amount was 11.4% and 4.21% respectively, and the proper lithium usage is the normal stoichiometric proportion, namely, the lithium amount is not excess.

The Study of Theoretic Coated Carbon Amount and Excess Lithium in LiFePO4/C Synthesis by Means of Carbon Thermal Reduction Route

Thin-walled parts are widely used in aerospace engineering. For their complexity under loading and the higher shape precision, it’s difficult for their manufacturing on high speed machine. In order to understand manufacture process, characteristic of aviation part in high speed machining is investigated. Error sources on parts are classified and the maximum error, dynamic errors are studied on its main influence factors, such as cutting force and vibration. Finally, useful method on cutting test part is proposed, which can observe and control dynamic accuracy of aviation part and ensure effective manufacture.

Study on Dynamic Accuracy of CNC in Aviation Part

In this paper, the bimodal amplitude-and frequency modulation method of atomic force microscopy (AFM) is applied to investigate the residual oil film on KDP crystal surface after polishing and surface cleaning. The thickness map of residual oil film is obtained based on the relationship between the cantilever resonant frequency shift and the surface stiffness. The thickness maps measured by AFM and spectroscopic imaging ellipsometry methods are compared, and the results obtained by two methods are consistent. The measurement scheme extends the application of AFM technology to characterize the residual oil on the KDP surface quality quantitatively after polishing and surface cleaning.

Wei Wang

Papers

Synthesis of LiFePO4/C Composite Cathode Materials by Solid State Method Using Mixed Iron Sources

Interaction Mechanism of Thermal and Mechanical Field in KDP Fly-Cutting Process

The Study of Theoretic Coated Carbon Amount and Excess Lithium in LiFePO4/C Synthesis by Means of Carbon Thermal Reduction Route

Study on Dynamic Accuracy of CNC in Aviation Part

Detection of Residual Oil Film on Polished KDP Crystal by Atomic Force Microscope