Maintenance, Reliability and Condition Monitoring
Not a member yet
1200 research outputs found
Sort by
Using total equivalent temperature difference approach to estimate air conditioning cooling load in buildings
Get PDFThe objective of this study is to provide a simplified worksheet based on the Total Equivalent Temperature Difference (TETD) Approach to estimate a building’s cooling load under Iraqi climate conditions. The heating, ventilation and air conditioning (HVAC) system was applied to scientific laboratories at the College of Engineering, University of Warith Al-Anbiyaa, Karbala, Iraq. The study estimates the cooling load of the building, which consists of 10 zones. Cooling load elements such as ventilation, lighting, walls, floors, roofs, windows, infiltration, and human factors were considered. The worksheet provides an appropriate alternative for easy and fast prediction within Iraq's climate conditions
Effect of damping ditch on blasting vibration reduction by field experiment and numerical simulation
Get PDFIn order to analyze the influence of a damping ditch on the blasting vibration, a large number of on-site monitoring tests with or without damping ditch were carried out based on the foundation pit excavation project. Based on the Sadovsky’s empirical formula, the optimized vibration velocity attenuation model was established by using the waveform subsection correspondence method and least square method. The calculation results are in good agreement with the measurement results. The average errors in radial direction and vertical direction are 17.04 % and 10.76 % respectively. A series of finite element models were established to study the influence of the damping ditch geometry on the damping effect. The experimental and numerical results show that the damping ditch can obviously reduce the blasting seismic effect, with the highest damping ratio in the area near blasting source. For different damping ditches, the damping ratio first increases and then decreases proportionally to the increase of distance between the measuring point and the blasting zone. The damping ditch depth has the best damping effect on blasting vibration, followed by the distance between the damping ditch and the blasting source, and finally the damping ditch width, which is consistent with the damping mechanism of theoretical analysis. The attenuation of the surface wave is only related to the damping ditch depth. The research results can provide a reference for the design of blasting vibration isolation
Experimental study of the lap motion trajectory of vibratory finishing machine
Get PDFVibratory equipment is widely used for performing various finishing processes, machining and forcing of different parts and materials. Numerous researchers and technologists pay specific attention to the possibilities of implementing vibration-driven machinery for conducting the lapping and polishing operations on flat surfaces. The present paper is dedicated to studying the laps kinematic parameters of the vibratory finishing machine actuated by six electromagnets. The paper’s scientific novelty consists in the experimental verification of the previously modelled and simulated circular trajectories of the laps under different operational conditions. The methodology of research contains two basic stages: changing the excitation frequency at the constant traction force and changing the traction force at the constant excitation frequency. The improved 3D-design of the vibratory finishing machine was developed in the SolidWorks software. The experimental prototype was implemented in practice, and full-scale tests were carried out using the WitMotion sensors and software. Based on the obtained experimental data, the trajectories of the machine’s laps were constructed and analyzed in the MathCad software. The research results substantiate the possibilities of providing circular oscillations of the laps at different operational conditions. The results can be used by technologists and engineers while choosing the appropriate design and control parameters for similar vibratory equipment intended for lapping and polishing of flat surfaces
The influence of the truss bar on the dynamic behavior of a Warren truss by changing the modulus of elasticity
Get PDFThe paper presents the natural frequencies shift of a Warren truss with seven elements in the case that members of the structure are weakened by considering that the modulus of elasticity with a lower value. Taking into consideration that the slenderness ratio has a constant value and the transverse section of the truss bars is changed, the relative frequency shift for the first seven vibration mode were calculated by using the values obtained from numerical modal analysis. The conclusions reveal the fact from the dynamic behavior of the structure it can be obtained templates to identify the weakened truss bar of the structure
Experimental study on stress wave propagation in jointed rock coupling the effect of JMC & JRC
Get PDFThe objective of this study is to experimentally investigate how the rough joints effect the stress wave propagation through jointed rocks coupling the effect of the joint matching coefficient (JMC) and joint roughness coefficient (JRC). The Split Hopkinson Pressure Bar (SHPB) apparatus was adopted to conduct uniaxial compression experiments on jointed specimens. The joint matching coefficient (JMC) and joint roughness coefficient (JRC) are introduced as morphology parameters to estimate joint roughness. Based on SHPB experiments, we found out that the joint matching coefficient (JMC) has a greater influence on the transmission and reflection coefficient than the joint roughness coefficient (JRC). Jointed specimens with lower JMC and JRC make less energy transmitted through it and have a smaller transmission coefficient and bigger reflection coefficients. Also, the joint with lower JMC and JRC has less initial stiffness and greater maximum closure
Vibration characteristics analysis of face gear transmission system considering gyroscopic effect
Get PDFTo improve the dynamics of the face gear transmission system, a nonlinear dynamics model considering gyroscopic effects and including parameters such as time-varying meshing stiffness, meshing damping, tooth side clearance, support stiffness and damping is developed. The Runge-Kutta method was used to solve the nonlinear kinetic equations and analyze the accuracy and reasonableness of the model calculation results. The vibration displacement, vibration velocity and vibration acceleration along each direction of the face gear and straight cylindrical gear were analyzed, and the torsional vibration characteristics of the center of mass of the two gears were studied
Construction and benchmark of an autonomous tracked mobile robot system
Get PDFRobots require a certain set of skills to perceive and analyse the environment and act accordingly. For tracked mobile robots getting good odometry data from sensory information is a challenging key prerequisite to perform in an unstructured dynamic environment, thus an essential issue in the tracked mobile robotics domain. In this article, we construct a ROS-based tracked mobile robot system taking the Jaguar V4 mobile robot as the base platform. On which several visual odometry solutions based on different cameras and methods (Intel RealSense T265, Zed camera, RTAB-Map RGBD) are integrated and benchmark comparison is performed. Analysis of new challenges faced by different methods while applied on a tracked vehicle as well as recommendations and conclusions are presented. Intel RealSense T265 solution proved to perform well in uncertain conditions which involves bounded vibrations and low lighting conditions with low latency, which result in good map generation. Further evaluations with a path planning algorithm and Intel RealSense T265 were conducted to test the effect of the robot’s motion profiles on odometry data accuracy
MPF based symmetric cipher performance comparison to AES and TDES
Get PDFThis paper presents a performance comparison of newly created matrix power function (MPF) based symmetric cipher realized in cipher-block chaining mode (CBC) with two other standardized ciphers namely AES-128 and triple DES. The encryption rate is compared using 64 bits arithmetic operations. It is shown that the proposed cipher has a significant advantage against compared ciphers. It is achieved by consuming more memory for MPF realization. Mentioned ciphers are compared using the central processing unit (CPU) the number of clock cycles required to encrypt fixed size plaintexts. This paper also includes a comparison of a number of operations required to encrypt plaintext as well as memory requirements for each of the ciphers with pre-determined parameters. The main difference between symmetric cipher based on MPF and other standardized ciphers mentioned in the paper is the ability to work with larger matrix entries in comparison to other algorithms as well as availability to parallelize the process of encrypting a single block
Structural mechanics analysis of bolt joint of rigid flexible coupling manipulator
Get PDFAs the key connecting part of the rigid flexible coupling manipulator, the structural dynamic characteristics of the bolted joint are analyzed by using the joint simulation technology of pro/e and ANSYS. Based on the spring equivalent principle, the finite element equivalent model of bolt joint is established, the relationship equation between contact surface pressure and bolt preload is derived, and its stress state is analyzed; Based on the micro convex deformation model and Hertz contact theory, the tangential stiffness equation and normal stiffness equation of the bolted joint are derived respectively. The three-dimensional model of the bolted joint is established by using pro/e and imported into ANSYS for joint simulation. The simulation experiments reveal the influence of bolt joint vibration characteristics under different conditions from the aspects of bolt diameter, pre tightening force, bolt group number and bolt distribution. The conclusions have important engineering value for the structural optimization of rigid flexible coupling manipulator
Design and noise-reduction simulation of an acoustic metamaterial plate incorporating tunable shape memory cantilever absorbers
Get PDFMetamaterials are materials having artificially tailored internal structure and unusual physical and mechanical properties. Due to their unique characteristics, metamaterials possess great potential in engineering applications. This study proposes a tunable metamaterial for the applications in acoustic isolation. Therefore, a stopband in the dispersion curve can be created because of the energy gap. For the conventional metamaterial, the stopband is fixed. Although the metamaterial with tunable characteristics has been proposed in the literature to extend its working stopband, the efficacy is usually compromised. In this study, cantilevers of tunable shape memory materials (SMM) via controlled phase transformation are incorporated into the metamaterial plate. Its theoretical finite element formulation for determining the dynamic characteristics is established. The effect of the configuration of the SMM cantilever absorbers on the metamaterial plate for the desired stopband in wave propagation is simulated by using finite element model and a commercial multi-physics software. The result demonstrates the tunable capability on the stopband of the metamaterial plate under different activation controls of the SMM absorbers, and shows the ability to trap the vibration at the designed frequency and prevent vibration wave from propagating downstream in different absorber arrangements and alloy phases. It should be beneficial to precision machinery and defense industries which have desperate need in vibration and noise isolation