Accepted Manuscripts

Amir M. Aboutaleb, Mark A Tschopp, Prahalad Rao and Linkan Bian
J. Manuf. Sci. Eng   doi: 10.1115/1.4037319
Despite recent advances in improving mechanical properties of parts fabricated by Additive Manufacturing (AM) systems, optimizing geometry accuracy of AM parts is still a major challenge for pushing this cutting-edge technology into the mainstream. This work proposes a novel approach for improving geometry accuracy of AM parts in a systematic and efficient manner. The proposed methodology formulates the geometric accuracy optimization problem as a multi-objective optimization problem. The developed method targeted at minimizing deviations within parts' major Geometric Dimensioning and Tolerancing (GD&T) features (i.e. Flatness, Circularity, Cylindricity, Concentricity and Thickness) from design specifications. The efficiency of proposed method is validated by conducting a real world case study for geometric accuracy optimization of parts fabricated by Fused Filament Fabrication (FFF) system. The results show that optimal designs are achieved by our methodology with fewer number of experiments compared with Full Factorial Design. Furthermore, we tested robustness of the proposed method via simulation studies. The proposed methodology is applied to test problems with various challenging characteristics such as non-convex Pareto front and congested design space, to name but a few. Simulation results and performance measures prove that the quality of Pareto front achieved by the proposed methodology is significantly higher compared with those resulted from Taguchi Design.
TOPICS: Pareto optimization, Additive manufacturing, Design, Optimization, Geometry, Cutting, Manufacturing, Simulation, Mechanical properties, Robustness, Simulation results, Geometric dimensioning and tolerancing
Kaifeng Wang, Daniel Shriver, Mihaela Banu, S. Jack Hu, Guoxian Xiao, Jorge Arinez and Hua-tzu Fan
J. Manuf. Sci. Eng   doi: 10.1115/1.4037320
Ultrasonic welding is a well-known technique for joining thermoplastics and has recently been introduced to joining carbon-fiber reinforced composites (CFRC). However, suitable models for predicting joint performance have not yet been established. At present, most failure models for bonded composites are built based on uniform adhesive joints, which assume constant joint properties. Nevertheless, the joint properties of ultrasonic spot welds for CFRC are variable, which depend on the input welding parameters. In this paper, the effect of welding energy, which is the most important welding parameter, on the joint properties is investigated first. Then a suitable surface-based lap-shear model is developed to predict the joint performance, wherein the critical fracture parameters in the model are described via the functions of welding energy. After comparing the simulated results with experiments, the model is proven feasible in predicting the joint properties of the ultrasonic spot welds.
TOPICS: Carbon fibers, Welded joints, Composite materials, Welding, Joining, Fracture (Materials), Fracture (Process), Failure, Shear (Mechanics), Adhesive joints, Ultrasonic welding
Jithin S, Upendra Bhandarkar and Suhas S. Joshi
J. Manuf. Sci. Eng   doi: 10.1115/1.4037322
Textured functional surfaces are finding applications in the fields of bioengineering, surface energy, hydrodynamics, lubrication and optics. Electrical discharge machining (EDM) which is normally used to generate smoother surface finish on various automotive components and toolings, can also generate surfaces of rough finish, a desirable characteristic for texturing purposes. There is a lack of modeling efforts to predict the surface textures obtained under various EDM operating conditions. The aim of the current work is to capture the physics of the electrical discharge texturing on a surface assuming random generation of multiple sparks with respect to i) space, ii) time, and iii) energy. A uniform heat disc assumption is taken for each individual spark. The 3D texture generated is utilized to evaluate a 3D roughness parameter namely arithmetic mean height, S_a. Surface textures obtained from the model are validated against experimentally obtained ones by comparison of distribution of R_a values taken along parallel sections along the surface. It was found that the distribution of simulated R_a values agree with that of experimental R_a values.
TOPICS: Simulation, Texture (Materials), Electrical discharge machining, Surface texture, Surface roughness, Finishes, Surface energy, Physics, Hydrodynamics, Lubrication, Heat, Optics, Bioengineering, Modeling, Disks
Brian W. Anthony and Fitriani Chua
J. Manuf. Sci. Eng   doi: 10.1115/1.4037234
Real-time algorithms are needed to compare and analyze digital videos of machines and processes. Techniques for the efficient dimensionality-reduction of, extraction of actionable-information from, and comparison of, videos will enable new opportunities in system monitoring and control. We define the Video Alignment Path (VAP) as the sequence of local time-and-space transformations required to optimally register two video-clips. We develop an algorithm, Dynamic Time and Space Warping (DTSW), which calculates the VAP. Measures of video-similarity, and therefore system-similarity, are estimated based on properties of the VAP. These measures of similarity are then monitored over time and used for decision making and process control. We describe the performance, structure, and computational complexity of a DTSW implementation which is parallelizable and which can achieve the processing rates necessary for many video-based industrial monitoring applications. We describe two case studies of unsupervised monitoring for mechanical wear and for fault detection. Results suggest opportunities for boarder applications of video-based instrumentation for real-time feedback control, wear and defect detection, or statistical process-control.
TOPICS: Machinery, Process control, Flaw detection, Algorithms, Wear, Instrumentation, Decision making, Feedback, System monitoring, Warping
Bayan Hamdan, Sarah Lafi and Noha M. Hassan
J. Manuf. Sci. Eng   doi: 10.1115/1.4037233
Carbon Fiber Reinforced Plastics (CFRPs) are sustainable materials compared to others due to their distinctive properties and light weight. On the other hand, producing CFRP products with minimum manufacturing costs and high quality can be quite challenging. This research aims to formulate a mathematical model that determines the optimum manufacturing process/processing parameters and takes into consideration the effect of the selected processes on the quality of panels and the environmental impact Surface roughness and percentage of voids are used as metrics to assess the desired quality level of the finished product. Energy consumption is used to quantify the environmental cost. Design of Experiment (DOE) was performed to study the effect of varying the process parameters, namely application method, pressure and temperature on the response variables. Regression models were used to model the response variables. A generalized model was developed and validated both numerically and experimentally. Results signify the need for a systematic approach to determine optimum manufacturing processes without resorting to trial and error.
TOPICS: Composite materials, Epoxy resins, Manufacturing, Carbon fibers, Surface roughness, Carbon reinforced plastics, Design, Sustainability, Energy consumption, Errors, Regression models, Plastics, Weight (Mass), Pressure, Temperature
Jianyi Li, Qian Wang, Panagiotis (Pan) Michaleris, Edward (Ted) Reutzel and Abdalla R. Nassar
J. Manuf. Sci. Eng   doi: 10.1115/1.4037235
There is a need for the development of lumped-parameter models that can be used for real-time control design and optimization for laser-based additive manufacturing (AM) processes. Our prior work developed a physics-based multivariable model for melt-pool geometry and temperature dynamics in a single-bead deposition for a directed energy deposition process, and then validated the model using experimental data from deposition of single-bead Ti-6AL-4V (or Inconel®718) tracks on an Optomec® Laser Engineering Net Shaping (LENS) system. In this paper, we extend such model for melt-pool geometry in a single-bead deposition to a multi-bead multi-layer deposition, and then use the extended model on melt-pool height dynamics to predict part height of a three-dimensional build. Specifically, the extended model incorporates temperature history during the build process, which is approximated by super-positioning the temperature fields generated from Rosenthal's solution of point heat sources, with one heat source corresponding to one bead built before. The proposed model for part height prediction is then validated using builds with a variety of shapes, including single-bead thin wall structures, a patch build and L-shaped structures, all built with Ti-6AL-4V using an Optomec® LENS MR-7 system. The model predictions on average part height show reasonable agreement with the measured average part height, with error rate less than 15%.
TOPICS: Geometry, Temperature, Lasers, Lenses (Optics), Dynamics (Mechanics), Heat, Physics, Design, Optimization, Real-time control, Errors, Shapes, Thin wall structures, Additive manufacturing
Kuo Liu, Haobo Liu, Te Li, Yongqing Wang, Mingjia Sun and Yuliang Wu
J. Manuf. Sci. Eng   doi: 10.1115/1.4037236
The conception of the comprehensive thermal error of servo axes is given. Thermal characteristics of a preloaded ball screw on a gantry milling machine is investigated, and the error and temperature data are obtained. The comprehensive thermal error is divided into two parts: TEE (thermal expansion error in the stroke range) and TDE (thermal drift error of origin). The thermal mechanism and thermal error variation of preloaded ball screw are expounded. Based on the generation, conduction, and convection theory of heat, the thermal field models of screw caused by friction of screw-nut pairs and bearing blocks are derived. The prediction for TEE is presented based on thermal fields of multi-heat sources. Besides, the influence factors of TDE are analyzed and the model of TDE is established based on least square method. The predicted thermal field of the screw is analyzed. The simulation and experimental results indicate that high accuracy stability can be obtained using the proposed model. Moreover, high accuracy stability can still be achieved even if the moving state of servo axis changes randomly, and the screw is preloaded and the thermal deformation process is complex. Strong robustness of the model is verified.
TOPICS: Screws, Errors, Milling machines, Servomechanisms, Stability, Heat, Temperature, Thermal expansion, Friction, Heat conduction, Simulation, Bearings, Convection, Robustness, Thermal deformation
Harish K. Nirala and Anupam Agrawal
J. Manuf. Sci. Eng   doi: 10.1115/1.4037237
Single Point Incremental Sheet Forming (SPISF) technique is an emerging process for die less forming. It has wide applications in many industries viz. automobile and medical bone transplants. Among several key parameters, toolpath planning is one of the critical aspects of SPISF. Also, Formability and geometric accuracy have been the two major limitations in SPISF. Spiral and constant incremental toolpaths and their variants have been investigated in detail by several researchers.Fractal based toolpath planning is also an attempt to improve the process of SPISF. Formability is measured in terms of thickness distribution and maximum forming depth achieved. This paper investigates a Fractal Geometry Based Incremental Toolpath (FGBIT) strategy to form a square cup using Incremental Sheet Forming (ISF). Fractal toolpath is a space-filling toolpath which is developed by fractal geometry theory. A comparison based study is conducted to observe the benefits of using FGBIT over traditional toolpaths (spiral and constant Z). Better formability, stress, and thickness distribution have been observed by adopting the proposed toolpath strategy. This toolpath strategy is new in its kind and has not been investigated in the metal forming domain. Experiments and simulations are conducted to validate the concept with reasonable accuracy.
TOPICS: Fractals, Geometry, Biomedicine, Metalworking, Simulation, Stress, Bone, Engineering simulation, Automobiles
Sepehr Nesaei, Mitch Darman Rock, Yu Wang, Michael Kessler and Arda Gozen
J. Manuf. Sci. Eng   doi: 10.1115/1.4037238
Conductive viscoelastic polymer composites (CVPCs) consisting of conductive fillers in viscoelastic polymer matrices find numerous applications in emerging technologies such as flexible electronics, energy storage, and biochemical sensing. Additive manufacturing methods at micro and meso-scales provide exciting opportunities towards realizing the unique capabilities of such material systems. In this paper, we study the direct-ink-writing (DIW) process of CVPCs consisting of electrically conductive additives in a poly(ethylene oxide) (PEO) matrix. We particularly focus on the deposition mechanisms of the DIW process and the influence of these mechanisms on the printed structure geometry, morphology, and functional properties. To this end, we utilized a novel practical approach of modeling the ink extrusion through the nozzles considering the non-newtonian viscous effects while capturing the viscoelastic extensional flow (drawing) effects through the variation of the nozzle exit pressure. We concluded that inks containing higher amounts of high molecular weight PEO exhibits drawing type deposition at high printing speeds and low inlet pressures enabling thinner, higher aspect ratio structures with ideal three-dimensional stacking. Under this deposition mechanism, the electrical conductivity of the anodic structures decreased with increasing printing speed, indicating the effect of the drawing mechanism on the printed structure morphology.
TOPICS: Composite materials, Elastomers, Inks, Additive manufacturing, Printing, Nozzles, Flexible electronics, Geometry, Molecular weight, Diluents, Energy storage, Modeling, Pressure, Electrical conductivity, Flow (Dynamics), Extruding, Fillers (Materials)
Barbara Linke, Ian Garretson, Francois M. Torner and Jörg Seewig
J. Manuf. Sci. Eng   doi: 10.1115/1.4037239
Grinding is an important abrasive machining process at the end of many process chains. Understanding energy transformation in grinding is not only important to improve energy efficiency, but it is crucial for understanding the chip formation process itself. Grinding energy can be studied at the macroscopic or microscopic levels, wherein the entire grinding tool is considered or the phenomena at the single cutting edges are studied. This paper explores existing energy modeling approaches in grinding with particular emphasis on physical models. Models on energy transformation during the ductile grit-workpiece engagement for three regimes – being friction, plowing, and shearing – are explained. In addition to the critical depth of cut when chip formation starts, a critical depth when plowing begins is introduced to divide between the different regimes. Selected models for each regime are combined to an integrated grinding energy model that allows researchers to investigate forces and energy during grit engagement.
TOPICS: Grinding, Friction, Modeling, Shearing (Deformation), Die cutting, Energy transformation, Cutting, Energy efficiency, Abrasive machining, Chain
Guoxu Yin and Ioan Marinescu
J. Manuf. Sci. Eng   doi: 10.1115/1.4037241
In the grinding process, high temperature in grinding area is generated by the frictional resistance between workpiece and abrasive grains on the grinding wheel cylindrical surface. Grinding fluid application is an optimal option to reduce the thermal effect and crack on the workpiece ground surface. In this paper, a grinding process heat transfer model with various grinding fluid application is introduced based on computational fluid dynamics (CFD) methodology. The effect of specific heat, viscosity and surface tension of grinding fluid are taken into account. In the model, the grinding contact area is considered as a heating resource. Most of the heat energy is conducted into the workpiece. The rest of the energy is taken away by the grinding wheel, grinding fluid and chips. How many percentage of the generated heat is conducted into the workpiece is a key issue. Namely, the energy partition ratio e. An energy partition equation is introduced in this paper with the cooling effect of different grinding fluid. Generated heat energy based on the calculation from energy partition equation is applied on the grinding contact area in the heat transfer model.
TOPICS: Heat transfer, Cooling, Fluids, Grinding, Heat, Computational fluid dynamics, Grinding wheels, Skin friction (Fluid dynamics), Temperature effects, Fracture (Materials), Viscosity, Heating, High temperature, Specific heat, Surface tension, Friction
Brian T. Gibson, Wei Tang, Artie G. Peterson, Zhili Feng and Gregory Frederick
J. Manuf. Sci. Eng   doi: 10.1115/1.4037242
A wear characterization study was performed to determine the useful lifetime of Polycrystalline Cubic Boron Nitride tooling for the friction stir welding (FSW) of stainless steel samples in support of a nuclear repair welding research and development program. In-situ and ex-situ laser profilometry were utilized as primary methods of monitoring tool geometry degradation, and volumetric defects were detected through both non-destructive and destructive techniques, as repeated welds of a standard sample configuration were produced. These combined methods of characterization allowed for the successful correlation of defect formation with tool condition. Additionally, the spectral content of weld forces was examined to search for indications of evolving material flow conditions, caused by significant tool wear, that would result in the formation of defects; this analysis established the basis for a system that would automatically detect these conditions. To demonstrate this type of system, an artificial neural network was trained and evaluated, and a 95.2% classification rate of defined defect states in validation was achieved. This performance constituted a successful demonstration of in-process monitoring of tool wear and weld quality in FSW of a high melting temperature, high hardness material, with implications for remote monitoring capabilities in the specific application of nuclear repair welding.
TOPICS: Friction, Wear, Welding, Stainless steel, Maintenance, Flow (Dynamics), Boron, Melting, Welding research, Welded joints, Artificial neural networks, Geometry, Tooling, Temperature, Lasers
Abhishek Ajri and Yung Shin
J. Manuf. Sci. Eng   doi: 10.1115/1.4037240
Setting optimum process parameters is very critical in achieving a sound friction stir weld joint. Understanding the formation of defects and developing techniques to minimize them can help in improving the overall weld strength. The most common defects in friction stir welding are tunnel defects, cavities and excess flash formation which are caused due to incorrect tool rotational or advancing speed. In this paper, the formation of these defects is explained with the help of an experimentally verified 3D finite element model. It was observed that the asymmetricity in temperature distribution varies for different types of defects formed during friction stir welding. The location of the defect also changes based on the shoulder induced flow and pin induced flow during friction stir welding. Besides formation of defects like excess flash, cavity defects, tunnel/wormhole defects, two types of groove like defects are also discussed in this paper. By studying the different types of defects formed, a methodology is proposed to recognize these defects and counter them by modifying the process parameters to achieve a sound joint for a displacement based friction stir welding process.
TOPICS: Computer simulation, Friction, Welding, Flow (Dynamics), Tunnels, Cavities, Displacement, Finite element model, Temperature distribution
Jan Kosmol
J. Manuf. Sci. Eng   doi: 10.1115/1.4037230
The paper presents a proposal about a method for analytical rolling friction coefficient determination. Basis of the proposal was an assumption: rolling friction coefficient is proportional to the semi-axes of the contact ellipses. The paper shows how to compute the semi-axes of the contact ellipses. The paper shows example results of contact loads identification using Finite Element Method and example of experimental results of friction torque as motion resistance of an angular bearing. Comparison of analytical and experimental determination of rolling friction coefficient was examined too.
TOPICS: Bearings, Rolling friction, Torque, Friction, Stress, Finite element methods
Wei Ji, Jinkui Shi, Xianli Liu, Lihui Wang and Steven Y. Liang
J. Manuf. Sci. Eng   doi: 10.1115/1.4037231
The high-efficiency utilisation of cutting tool resource is closely related to the flexible decision of tool life criterion, which plays a key role in manufacturing systems. Targeting a flexible method to evaluate tool life, this paper presents a data-driven approach considering all the machining quality requirements, e.g. surface integrity, machining accuracy, machining stability, chip control, and machining efficiency. Within the context, to connect tool life with machining requirements, all patterns of tool wear including flank face wear and rake face wear are fully concerned. In this approach, tool life is evaluated systematically and comprehensively. There is no generalised system architecture currently, a four-level architecture is therefore proposed. Workpiece, cutting condition, cutting parameter and cutting tool are the input parameters, which constrain parts of the independent variables of the evaluation objective including first-level and second-level indexes. As a result, tool wears are the remaining independent variables, and they are calculated consequently. Finally, the performed processes of the method are experimentally validated by a case study of turning superalloys with a PCBN cutting tool.
TOPICS: Wear, Machining, Cutting tools, Cutting, Manufacturing systems, System architecture, Superalloys, Stability
Zhongde Shi, Amr Elfizy, Helmi Attia and Gilbert Ouellet
J. Manuf. Sci. Eng   doi: 10.1115/1.4037183
This paper reports an experimental study on grinding of chromium carbide coatings using electroplated diamond wheels. The work was motivated by machining carbide coatings in gas turbine engine applications. The objective is to explore the process conditions and parameters satisfying the ground surface quality requirements. Surface grinding experiments were conducted with water based grinding fluid on chromium carbide coated on flat surfaces of aluminum blocks for rough grinding at a fixed wheel speed vs = 30 m/s, and finish grinding at vs = 30, 60 m/s. The effects of depth of cut and workspeed on grinding power, forces, and surface roughness were investigated for each of the wheel speeds. Material removal rate Q = 20 mm3/s for rough grinding at a grinding width b = 101.6 mm was achieved. It was found that the maximum material removal rate achievable in rough grinding was restricted by chatters, which was mainly due to the large grinding width. The specific energy ranged from 27 to 59 J/mm3 under the tested conditions. Surface roughness Ra = 3.5- 3.8 µm were obtained for rough grinding, while Ra = 0.6 - 1.5 µm were achieved for finish grinding. Surface roughness was not sensitive to grinding parameters under the tested conditions, but was strongly dependent on the diamond grain sizes. Imposing axial wheel oscillations to the grinding motions reduced surface roughness by about 60% under the tested condition. It was proved that it is feasible to grind the chromium carbide coating with electroplated diamond wheels.
TOPICS: Coatings, Grinding, Diamonds, Wheels, Surface roughness, Finishes, Gas turbines, Oscillations, Fluids, Aluminum, Machining, Surface quality, Grain size, Water
Yanfeng Xing
J. Manuf. Sci. Eng   doi: 10.1115/1.4037106
Fixture layout can affect deformation and dimensional variation of sheet metal assemblies. Conventionally, the assembly dimensions are simulated using a large number of finite element analyses, and fixture layout optimization needs significant user intervention and unaffordable iterations of finite element analyses. This paper therefore proposes a fully automated and efficient method of fixture layout optimization based on the combination of 3DCS simulation (for dimensional analyses) and global optimization algorithms. In this paper, two global algorithms are proposed to optimize fixture locator points, which are social radiation algorithm (SRA) and GAOT, a genetic algorithm in optimization toolbox in MATLAB. The flowchart of fixture design includes the following steps: (1) The locating points, the key elements of a fixture layout, are selected from a much smaller candidate pool thanks to our proposed manufacturing constraints based filtering methods and thus the computational efficiency is greatly improved. (2) The two global optimization algorithms are edited to be used to optimize fixture schemes based on MATLAB. (3) Since MATLAB macro commands of 3DCS have been developed to calculate assembly dimensions, the optimization process is fully automated. A case study of inner hood is applied to demonstrate the proposed method. The results show that the GAOT algorithm is more suitable than SRA for generating the optimal fixture layout with excellent efficiency for engineering applications.
TOPICS: Sheet metal, Design, Optimization algorithms, Optimization, Matlab, Manufacturing, Algorithms, Dimensions, Finite element analysis, Genetic algorithms, Engineering systems and industry applications, Dimensional analysis, Deformation, Filtration, Radiation (Physics), Simulation
Renwei Liu, Zhiyuang Wang and Frank Liou
J. Manuf. Sci. Eng   doi: 10.1115/1.4037107
In recent years, the usage of additive manufacturing (AM) provides new capabilities for component repair, which includes low heat input, small heat-affected zone, and freeform near-net-shape fabrication. Because the geometry of each worn component is unique, the automated repair process is a challenging and important task. The focus of this paper is to investigate and develop a general best-fit and shape adaption algorithm for automating alignment and defect reconstruction for component repair. The basic principle of using features for rigid-body best-fitting is analyzed and a multi-feature-fitting method is proposed to best-fit the 3D mesh model of a worn component and its nominal component. The multi-feature-fitting algorithm in this paper couples the least square method and a density-based outlier detection method. These two methods run alternately to approach the best-fit result gradually and eliminate the disturbance caused from the defect geometry. The shape adaption algorithm is used to do cross-section comparison and defect reconstruction based on the best-fitted 3D model. A 'point-line-surface' fracture surface detection method is proposed to construct fracture surface and the fracture surface boundary is dilated to trim the nominal 3D model to obtain defect geometry. Illustrative examples with typical components and different kinds of defects are used to demonstrate the flexibility and capability of using multi-feature-fitting and shape adaption algorithm developed in this paper.
TOPICS: Maintenance, Algorithms, Fittings, Shapes, Fracture (Materials), Geometry, Fracture (Process), Heat, Three-dimensional models, Additive manufacturing, Density, Manufacturing
Luis Otavio B S Alves, Rodrigo S Ruzzi, Rosemar Batista da Silva, Mark Jackson, Gilson Eduardo Tarrento, Hamilton José de Mello, Paulo Roberto de Aguiar and Eduardo Carlos Bianchi
J. Manuf. Sci. Eng   doi: 10.1115/1.4037041
In general high volume of coolant are required because of large amount of heat generated in grinding. On the other hand, environmental impacts and human health problems caused by coolants have been a key issue towards sustainable manufacturing. Thus, is important to seek for strategies to reduce the volume of fluids and their risks as well as guarantee grinding efficiency. A possible solution for this problem is to use the MQL technique with an auxiliary compressed air system to clean the grinding wheel during machining. In this context, this work evaluated the performance of the MQL technique with grinding wheel cleaning in relation to the conventional cooling techniques (flood cooling) during a cylindrical plunge grinding of N2711 steel. N2711 steel is widely employed in manufacturing of molds for plastic injection processes and is one of steels more susceptible to grinding burn. The following output parameters were used to assess the performance: surface roughness, roundness, microhardness, grinding power and grinding wheel wear. The results showed that the MQL technique provided superior workpiece quality and lower power consumed compared to the flood technique. The MQL technique proved to be an alternative method compared to the conventional technique under the conditions investigated. Also, Malkin's model was used to predict the grinding ratio (G-ratio) based on experimental data obtained in this work. After regression analysis, the model predicted the G-ratio from the specific material removal rate and the cutting speed with a satisfactory accuracy of approximately 92%.
TOPICS: Steel, Grinding, Grinding wheels, Performance evaluation, Floods, Coolants, Manufacturing, Cooling, Fluids, Machining, Wear, Heat, Surface roughness, Microhardness, Sustainability, Cutting, Regression analysis, Compressed air
Shibin Wang, Laihao Yang, Xuefeng Chen, Chaowei Tong, Baoqing Ding and Jiawei Xiang
J. Manuf. Sci. Eng   doi: 10.1115/1.4036993
Vibration signal analysis has been proved as an effective tool for condition monitoring and fault diagnosis for rotating machines in the manufacturing process. The presence of the rub-impact fault in rotor systems results in vibration signals with fast oscillating periodic instantaneous frequency (IF). In this paper, a novel method for rotor rub-impact fault diagnosis based on nonlinear squeezing time-frequency transform (NSquTFT) is proposed. Firstly, a dynamic model of rub-impact rotor system is investigated to quantitatively reveal the periodic oscillation behavior of the IF of vibration signals. Secondly, the theoretical analysis for the NSquTFT is conducted to prove that the NSquTFT is suitable for signals with fast varying IF, and the method for rotor rub-impact fault diagnosis based on the NSquTFT is presented. Through a dynamic simulation signal, the effectiveness of the NSquTFT in extracting the fast oscillating periodic IF is verified. The proposed method is then applied to analyze an experimental vibration signal collected from a test rig and a practical vibration signal collected from a dual-rotor turbofan engine for rotor rub-impact fault diagnosis. Comparisons are throughout conducted to evaluate the effectiveness of the proposed method by using Hilbert-Huang transform, wavelet-based synchrosqueezing transform, and other methods. The application and comparison results show that the fast oscillating periodic IF of the vibration signals caused by rotor rub-impact faults can be better extracted by the proposed method.
TOPICS: Fault diagnosis, Rotors, Signals, Vibration, Condition monitoring, Theoretical analysis, Wavelets, Dynamic models, Turbofans, Oscillations, Machinery, Engines, Manufacturing, Simulation

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