FATIGUE STRENGTH OF A CHASSIS OF A SEMI-HEAVY TRUCK UNDER DYNAMIC LOADS DUE TO REAL ROAD ROUGHNESS

Evaluation of fatigue life of vehicles by using a real road test is very expensive; therefore, numerical methods such as Finite Element Method (FEM) are nowadays very popular for evaluating fatigue life. In this study, a method based on FEM is proposed for predicting fatigue strength of the chassis when designing and optimizing a semi-heavy truck. An experimental modal analysis has been applied for the validation of the finite element model which has been used in the proposed method. The natural frequencies and mode shapes of the chassis have been obtained from the finite element analysis and compared with the corresponding results of the experimental modal analysis. Also, a method for producing uneven roads in the time domain based on the International Reference Index (IRI) was introduced to simulate road roughness. In addition, different road types (with potholes and kerbs) and different load conditions (braking and cornering) have been considered throughout the simulation. In all of the mentioned conditions, stress time histories have been extracted and investigated. Finally, fatigue damage and strength of the chassis and welded connections have been estimated and described

Modal analysis of the vertical moving table of 4-DOF parallel machine tool by FEM and experimental test

The vibration of the machine tool has important effect on machining quality of parts. So, in this paper, the dynamic behavior and modal parameters of the vertical moving table of the 4-DOF parallel machine tool are studied using the FEM and experimental methods. The prepared model of the vertical moving table in Solidworks is exported to ANSYS environment. Then, its natural frequencies and mode shapes are extracted using the modal analysis. Then having the FEM results, the exact modal data of the vertical moving table is obtained by the experimental tests. The exciting conditions of the machine tool table are obtained through modeling of machining operations. Finally, the resonance situations of the table are found using the modal data of the table and the cutting parameters of the machine tool. The results of this research can help the machine tool operator to avoid the vibration condition through correct selection of the cutting parameters

Exact uncertainty analysis of the bridge dynamic response during random vehicle crossing by statistical methods

Modeling and simulation of the bridge response during vehicle moving on it is very important in optimum bridge design. There are many researches in this field which some of them deals with studying of the structure and bridge uncertainty effects on the bridge-vehicle dynamic response. Some researchers are dealing with vehicle uncertainty that is uncertainty in mass, sprung, damping, velocity, numbers, incoming time and other mechanical parameters of the vehicles. Other researchers are considering the bridge parameters uncertainty like as module of elasticity, bearing immobility and mass of the bridge. Also in most of the researches, analytical and Monte-Carlo simulations have been used for obtaining the dynamic response of the bridge with considering mentioned uncertainty. However there isnât any accurate and general statistical study on the bridge response with general uncertainty. In other words, the complete set of uncertainty of the vehicles or bridge has not been applied in modeling and also the exact statistical study of the dynamic response of the bridge has not been applied exactly. Therefore in this paper, after modeling of the bridge-vehicle system with coupled finite element beam and discrete vehicle model, most of the uncertainties of the vehicles have been produced with Gaussian probability distribution function and the statistical parameters of the response have been extracted by Monte-Carlo simulation. The selected model applied in this paper is a discrete model of vehicle with four degree of freedom mass sprung system. Also, the Euler-Bernoulli model was used for bridge and the coupled dynamic equation was extracted using finite element modeling of the beam with Hermitian interpolation function for suitably dividing the vehicle forces, applied on the beam elements nodes. In addition the different road surface using ISO standard was applied on the finite element beam model. One of the major contributions of this paper is considering the type of the vehicle crossing on the bridge as an additional uncertain parameter which is not mentioned in the previous literatures. In other words, three classes of the vehicle that is heavy, semi-heavy and light ones was applied in simulation as uncertain parameters. The mechanical characteristics of the vehicle were derived by CARSIM software and by Monte-Carlo simulation using uniform probability distribution function. Then mentioned parameters was produced and entered in New-Mark simulation steps. With studying on the deflection, velocity, acceleration of the bridge and also considering corresponding upper and lower limit band (confidence interval) and variance of the mentioned parameters, extended results of uncertainties effects have been obtained. It should be mentioned, in this paper an exact statistical test method was used for obtaining the statistical properties of the dynamic response. Also, in different road surface and conditions, the simulation was carried out such that four surfaces of the bridge and three type of the vehicle classes was simulated separately and finally one simulation was done in complete set of the uncertainty. Very detailed and complete results were studied and one of the important results of this paper is reporting the most effective uncertainties on the bridge response. As one of the results, it was found that with increasing the velocity of the vehicle, surface roughness and weight of the vehicle, the uncertainty of the response are increasing. As another important result is that the fundamental frequencies of the bridge is less sensitive to the uncertainties of the vehicles' parameters. Derived results of this paper can be applied in optimum designs of the bridges and also in designing the damage identification methods

Damage Detection of Gantry Crane with a Moving Mass Using Artificial Neural Network

Gantry cranes play a pivotal role in various industrial applications, and their reliable operation is paramount. While routine inspections are standard practice, certain defects, particularly in less accessible components, remain challenging to detect early. In this study, first a finite element model is presented, and the damage is introduced using random changes in the stiffness of different parts of the structure. Contrary to the assumption of inherent reliability, undetected defects in crucial structural elements can lead to catastrophic failures. Then, the vibration equations of healthy and damaged models are analyzed to find the displacement, velocity, and acceleration of the different crane parts. The learning vector quantization neural network is used to train and detect the defects. The output is the location of the damage and the damage severity. Noisy data are then used to evaluate the network performance robustness. This research also addresses the limitations of traditional inspection methods, providing early detection and classification of defects in gantry cranes. The study’s relevance lies in the need for a comprehensive and efficient damage detection method, especially for components not easily accessible during routine inspections

TLP Structural Health Monitoring Based on Vibration Signal of Energy Harvesting System

Abstract Structural Health Monitoring (SHM) of Tension Leg Platform (TLP) is very crucial for preventing catastrophic and sudden collapse of the structures. One of the methods of monitoring these structures is implementing SHM sensors. Supplying energy for these sensors for a long period is a challenging problem. So, one of the new methods of supplying energy for SHM, is usage of mechanical energy. In this method, the piezoelectric material is employed to convert the mechanical energy which is resulted from vibration of structure, to electrical energy. The advantage of this method is based on not implementing the battery charging system. Therefore, in this paper, after modeling TLP structure, energy supplying of these sensors with piezoelectric converters is studied. Furthermore, fault diagnosis of these structures in the presence of different uncertainties is proposed by the features of voltage signal, produced from piezoelectric patches and fuzzy classification method. Results show that this method can diagnose faults of the structure with an acceptable success rate

A study on vibration of Setar: stringed Persian musical instrument

Knowing how a musical instrument vibrates can benefit the tonal characteristics shaping of the instrument. In this research, an approach for investigating the mode shapes and natural frequencies of Setar body is addressed. First, mechanical properties of wood used in the production of Setar are analyzed experimentally. Then a numerical modal test is performed to find the mode shapes and natural frequencies of Setar structure. To validate the results obtained by the numerical method, experimental modal testing is also done for the structure, and it is found that the results of both the methods are in good consistency. As the vibration pattern of plates is of utmost importance in the production of musical instruments, vibration patterns of a Setar plate are experimentally extracted and the results are compared with finite element analysis