Papers by Keyword: Vibration

Abstract: Fused deposition modeling (FDM) or 3D printing is one of the promising techniques widely preferred to fabricate complex and customized 3D objects or prototypes for various engineering and non-engineering applications. With the growing demands of customized prototypes, researchers are facing a major challenge for maintaining effective part quality with adequate surface finish and strength; and minimizing the cost, defects, and waste in 3D printing. Condition monitoring is one of the strategies to achieve the aforementioned. It has a huge potential to minimize defects and print failures in 3D printing. The main objective of this research work is to perform online condition monitoring of the nozzle status with the help of vibration signals in fused deposition modelling process. The effect of nozzle clogging on the consistency of material deposition and its effect on surface finish has experimentally investigated in this work. The set of experiments were performed by artificially creating the condition of nozzle clogging to investigate the effect of nozzle clogging on print quality (surface finish). Nozzle clogging condition was created by increasing the feed rate of polylactic acid (PLA) filament at a low heat supply rate to the nozzle by modifying the commands of 3D printer. The layer thickness was varied throughout the experiments to observe the nozzle clogging. The vibrations signals were acquired by using an accelerometer that was mounted near the nozzle. The data acquisition frequency of the accelerometer was 12500Hz. Further, the acquired vibration signals were analyzed using the Fast Fourier transformation (FFT) signal processing technique. Results revealed that nozzle clogging severely affects surface quality and geometrical accuracy of the fabricated 3D part due to nozzle vibration and non-uniform material deposition. Moreover, nozzle clogging and its relevant consequences like non uniform material deposition can be monitored using vibration signal-based condition monitoring during part fabrication and based upon that appropriate measures can be taken for defects and waste elimination.

Abstract: The rheological properties of concrete have a great impact on the workability, and the L-box test can obtain the relationship between the morphology and the yield value of the material under free flow conditions. However, as an elastoplastic fluid, the low water-cement ratio concrete can hardly flow freely without the admixture. The vibrating process is often used in the production to meet the requirements, but the rheological properties of the material under vibration are difficult to measure. A new vibration test method for the flowability of low water-cement ratio concrete is proposed in combination with the L-box idea. The flow morphology and flow velocity of two kind of low water-cement ratio concrete in the L-box are observed under the condition of controlling the vibration frequency. After that, theoretically analyzing the yield value of the material under vibration is applied. The results show that with the increase of vibration frequency, the average flow velocity of the material increases, but the trend is gradually slower. With the increase of vibration frequency, the yield value of low water-cement ratio concrete is much lower than before. This test method can be used in related engineering applications of vibrating compacted concrete.

Abstract: In cutting process, the wear of the tool remains posed, it describes their progressive failure in regular operation. The tool wear phenomena is mainly caused by abrasion of hard particles, shearing of micro welds between tool and work-material and the exchange of particles between the tool and work material leading to a several forms of tool wear, however, we focused in this study on the frontal wear, also called wear on clearance surface or flank wear. For efficient use of cutting tool according to the technical requirement, the comprehension and the knowledge of the cutting tool wear evolution is necessary. In order to meet this indispensable need, the present paper proposes a two-step tool flank wear monitoring technique based on vibratory signals analysis during the turning operation using a P30 grade metal carbide tool and C45 (XC48) steel. Firstly, discrete wavelet transforms (DWT), has been used to decompose the signal and extract the information, then the scalar indicator Root Mean Square (RMS) value has been used to evaluate the cutting tool stability level. The proposed method offers the possibility to accurately predict break-in tool wear phase, accelerated tool wear phase and the stability period, in which a high quality machining process is guaranteed.

Abstract: This research presents a dynamic analysis of a large-scale hydraulic cylinder actuator via numerical simulation. A model of the actuator built with dynamically parameters is implemented basing on fluid mechanics and vibration theories. In which, coefficients of viscous damping and stiffness generated by compressibility and viscous characteristics of hydraulic oil are considered. Hence, the large-scale hydraulic cylinder actuator can be investigated via an equivalent model of mass-spring-damper. In order of obtaining the system response, numerical simulation is done with some realistic actuator parameter sets. The results are consistent with reality and can be used as valuable fundamental for large-scale hydraulic cylinder actuator design.

Abstract: This paper examines the characteristics of stick-slip phenomena between the glass plate and Magneto-Rheological Elastomer (MRE) surface. Stick-slip phenomena are the spontaneous jerking motion that occurs while two objects are sliding over each other, usually accompanied by noise. Stick-slip is generated when it involves discontinuous frictional degradation when moving from static friction to dynamic friction. The phenomena can lead to uneven wear patterns, vibration and squeal noise which cause a shorter lifespan for the corresponding mechanical elements. MREs are kind of function materials to consist of a polymeric matrix with embedded ferromagnetic particles. Mechanical properties of the MREs can be controlled by the application of magnetic fields. The magnetic field-based controllability can be applied to the control of stick-slip phenomena. The friction experiment is conducted with the Reciprocating Friction Tester (RFT). The sliding speed of the RFT should be in low-speed conditions in order to make the stick-slips relatively easy to occur. A uniform magnetic field and a weight load are applied to the MRE sample to observe the effect of various experimental parameters on the movement of the stick-slip. In addition, frictional sounds due to the stick-slip phenomenon under different loads and magnetic field strength are measured and analyzed. The results of this experiment show that as the strength of the magnetic field increases, the difference in stiffness between the wipers-glass decreases, mitigating fricatives. The result is expected to be well applied to low-noise automotive wipers based on the controllability of friction behavior and squeal noise.

Abstract: In this study, Fast Fourier Transform (FFT) was used in order to detect bore hole in a structure. FFT is a common method in digital signal processing (DSP) to characterize the frequency emitted by some structure. This method is widely used because of its simplicity. Computational time needed for FFT is relatively lower than another method. The use of FFT to analyze defect in structure is not commonly used since FFT has some weakness for example spatial frequency cannot be extracted to point out the defect location. In this paper, defect was designated as a hole in a strip iron plate with 20 mm in diameter. The strip iron plate was 1 meter long, 38 mm wide and 3 mm thick. This strip iron plate was clamped at one of its ends while the other side is left free. In order to produce vibration signal, impact hammer Bruel Kjaer Type 8202 was used with plastic tip to limit the vibration frequency in to the range of 0 - 1000 Hz. The trigger point was 30 mm from its free end. Three accelerometers were placed series in one line with the trigger point with 300 mm distance of each accelerometer. The position of the hole was varied in three different position. The first position was between trigger point and first accelerometer, between first and second accelerometer and between the second and third accelerometer. The raw signal obtained from the accelerometer was processed by using FFT to understand the mode shape changes in the strip iron plate due to the bore hole. Furthermore, the FFT result was analyzed as function of receiver position to determine the position of hole. The result shows that the frequency characters were different in each case and further analysis by using magnitude-squared coherence function need to be used in order to quantitatively find the difference between FFT result.

Abstract: In the framework of this study, compressed earth blocks (CEB) were produced using waste materials and various parameters. Material parameters included waste soil, recycled concrete, fly ash, cement, admixtures and water contents. Manufacturing parameters were vibration during manufacturing, confinement pressure, curing environment and curing time. Specimens used in this study were cubes and compressive strength testing was used to evaluate different mixtures and manufacturing methods. In terms of compressive strength, compressed earth blocks made of these materials could be used for manufacturing bricks and other structural elements.

Abstract: Strong earthquake affects buildings to response in huge dynamic oscillating motion. In a teaching hospital that full of patients, medical personnel and medical treatment facilities as well as many modern advanced equipment may be in very dangerous situation due to this building response. To reduce the human victims, equipments and infrastructure damages, a kind of base isolation is added to the foundation of the hospital building. Inspite of oscillation motion as a vertical cantilever, this foundation base isolation of the hospital building is applied and designed to give the response of the earthquake vibration waves in lateral motion. To find out the optimum properties of the base isolation, some calculations of the response from vibration parameters are observed. The K_eq value is 415,120,000 N/m and the total massive Mass of the hospital is 148,057,364 kg as well as the highest vibration force is 108,136,030.2 N. This study work deals with simplified modelling using FEA in ANSYS software. The aim is to see the simulation based on the calculation of the analysis and whether the response is as expected.

Abstract: This paper deals with a mathematical model of thermoelastic rectangular nano-beam, which is thermally loaded by thermal shock and subjected to moving heat source with constant speed. The nano-beam has been clamped-clamped and its length along the x-axis. The governing equations have been written by using the Euler–Bernoulli equation of nano-beams and the non-Fourier heat conduction with one-relaxation time. Laplace transform has been applied with respect to the time variable, and the solutions have been derived in its domain. The numerical solutions for the Silicon material have been done by using Tzou method. The results have been shown in figures for the temperature increment and the lateral deflection with various values of heat source speed to stand on its effects. Moreover, the effects of the ratio between the length and the width of the beam have been discussed. The speed of the heat source and the dimensions of the beam have significant effects on the temperature increment and the lateral deflection of the beam.

Abstract: This paper presents an investigation of the size-dependent static and dynamic characteristics of functionally graded (FG) Timoshenko nanobeams embedded in a double-parameter elastic medium. Unlike existing Timoshenko nanobeam models, the combined effects of surface elasticity, residual surface stress, surface mass density and Poisson’s ratio, in addition to axial deformation, are incorporated in the newly developed model. Also, the continuous gradation through the thickness of all the properties of both bulk and surface materials is considered via power law. The Navier-type solution is developed for simply supported FG nanobeam in the form of infinite power series for bending, buckling and free vibration. The obtained results agree well with those available in the literature. In addition, selected numerical results are presented to explore the effects of the material length scale parameter, surface parameters, gradient index, elastic medium, and thickness on the static and dynamic responses of FG Timoshenko nanobeams.