Experimental verification of parameters in automobile crankshaft modelling for vibration analysis

In the interest of utilized more stable automobile components at high speed for reduction the vibration of mechanical system, dynamic characteristics analysis plays a vital role in complex mechanical parts. This paper introduces a clarified approach on statistical investigation and modal analysis methodology to study, predict and accurate crankshaft natural frequencies by using design of experiment (DOE). In this research, first, simulation had been done with MSC Nastran/ Patran to find out the natural frequencies in each mode shape of crankshaft as well as the verification with experiment was carried out. In order to less inaccuracy, numerous simplified crankshaft models were created by using these as input and DOE was established to acquire precise parameters of optimized crankshaft design as the second phase. This method can be further used for the optimizing the structural parameters and would provide some value basis to qualitative measure of parameters and determination of optimized structure. In Conclusion, modal verification accuracy between experimental and simulation has improved

Développement de formulations analytiques pour déterminer la réponse dynamique de plaques composites immergées soumises à des explosions sous-marines

Underwater explosions involve many complex physical phenomena such as shock wave propagation, fluid-structure inter actions, cavitation, etc. To model these phenomena as precisely as possible, finite element calculations coupled with the code "Underwater Shock Analysis" (USA) are used nowadays. However, such approaches require a lot of modeling effort and computation time. In this context, the research work carried out within the framework of this thesis has enabled the development of simplified analytical formulations that are both rapid and reasonably accurate. The range of validity of the proposed formulations was examined by comparing the analytical results with numerical simulations (also carried out within the framework of the thesis) and experimental results available from the literature. An office design tool for the analysis of the shock response of submerged composite plates was also developed.Les explosions sous-marines comprennent de nombreux phénomènes physiques complexes tels que la propagation des ondes de choc, les interactions fluide structure, la cavitation, etc. Pour modéliser ces phénomènes aussi précisément que possible, des calculs par éléments finis couplés au code ‘Underwater Shock Analysis’ (USA) sont aujourd’hui utilisés. Cependant, de telles approches nécessitent beaucoup d'efforts de modélisation et de temps de calcul. Dans ce contexte, le travail de recherche réalisé dans le cadre de cette thèse a permis de mettre au point des formulations analytiques simplifiées à la fois rapides et raisonnablement précises. Le domaine de validité des formulations proposées a été précisé en confrontant les résultats analytiques à des simulations numériques (réalisées également dans le cadre de la thèse) et des résultats expérimentaux issus de la littérature. Un outil de bureau d’étude pour l’analyse de la réponse au choc de plaques composites immergées a également été développé

On the applicability of Taylor’s theory to the underwater blast response of composite plates

International audienceThe response of a plane, air-backed plate attached to a rigid baffle when subjected to an underwater plane shock wave is investigated numerically and analytically. The numerical simulation takes into account a full threedimensional fluid model involving water cavitation effects. Different numerical models are employed and validated by comparing against various experimental results from the literature. The validated numerical setup is then used to simulate the underwater shock response of simply-supported, air-backed, carbon-fiber/epoxy rectangular plates attached to a rigid baffle. Simplified analytical solution is developed based on two-step approach. The two stages considered are early-time phase that adapts Taylor’s fluid-structure theory to calculate an impulsive velocity for the plate and long-time phase that involves determining its free oscillation response withinlinear elastic domain, taking into account the water-added mass effect. Finally, the applicability of the proposed method is investigated by performing different numerical simulations regarding various combinations of peak pressures and decay times, change of aspect ratios, change of materials as well as ply orientations

Development of Analytical Formulae to determine the Response of Submerged Composite Plates subjected to Underwater Explosion

International audienceClosed-form analytical formulae are developed to analyze the bending response of submerged composite rectangular plates subjected to underwater explosions (UNDEX). These explosions are supposed to occur at a sufficiently large stand-off distance so that a uniformly distributed pressure pulse can be applied and the corresponding bubble effects can be ignored. The plate is considered in an air-backed condition. The derivation steps are divided into two main stages. In the first stage, the impulsive velocity due to the interaction of shock wave and structure is determined by using Taylor's fluid-structure interaction (FSI) formulation while supposing a negligible structural deformation. Transmission of shock waves through the thickness of the plate is considered by assuming the material under uniaxial strain. At the end of the first stage, cavita-tion is supposed to occur all over the plate. In the second stage, deformation of the plate will commence which is followed by the collapse of the cavitation zone. The corresponding mechanical response of the plate is determined by imposing a simply-supported boundary conditions and by applying Lagrangian Energy approach to derive the motion equation, taking into account the water inertial effects. The proposed method is then tested with isotropic (steel) and laminated composite (carbon-fiber/epoxy) plates to analyze for both impulsive velocity and UNDEX responses. The obtained analytical results are compared with those from non-linear finite element explicit code, LS-DYNA. Finally, the advantages and limitations of the present method are evaluated

Response of composite plates in air-backed and water-backed conditions subjected to a far-field underwater explosion

International audienc

Application of Lagrangian Energy Approach to determine the Response of Isotropic Circular Plates subjected to Air and Underwater Blasts

International audienceThis paper presents a simplified analytical formulation that uses Lagrangian Energy Approach to predict air and underwater blast response of air-backed simply-supported circular steel plates. Triangular and exponential pressure profiles are considered for air and underwater blast loading respectively. Calculation of the response is divided into two stages. In the first stage, maximum impulsive velocity is determined by assum-ing that the plate has negligible deformation and then by using the conservation of linear momentum for air blast and Taylor’s one-dimensional analytical model for underwater blast. In the second stage of calculation, elastic deformation is obtained by applying the initial conditions determined from the first stage, also taking into account the rotatory inertia and water-added inertia effect. The obtained analytical solutions are tested with various plate aspect ratios as well as various loading levels and the results are compared with those from non-linear finite element explicit simulations. It is found that the proposed formulations correlate well with the finite element results giving only 5–20% discrepancy provided that the plate deflections are supposed to remain small compared to its thickness. Finally, the advantages and limitations of the present method are discussed

A coupled closed-form/Doubly Asymptotic Approximation approach for the response of orthotropic plates subjected to an underwater explosion

International audienceIn this paper, a closed-form analytical solution procedure is proposed to solve the coupled fluid-structure interaction (FSI) equations that involve the first-order Doubly Asymptotic Approximation (DAA1) formulation. An efficient method comprised of the nonstandard finite difference (NSFD) scheme is applied. First of all, analytical equations are developed to analyze the response of a rigid mass-spring oscillator in an air-backed condition when it is subjected to a plane shock exponential wave coming from a far-field underwater explosion. After validating the results with LS-DYNA/USA (DAA1), these equations are extended to determine the response of a two-dimensional, simply-supported rectangular plate, and then tested on the isotropic and orthotropic plates within a small deflection regime. Parametric studies are also performed by varying the load decay times, peak pressures, as well as the aspect ratios of the plate. Finally, the advantages and limitations of the proposed formulae are exposed along with suggestions for the future work

Response of composite plates in air-backed and water-backed conditions subjected to a far-field underwater explosion

International audienc

Application of Lagrangian Energy Approach to determine the Response of Isotropic Circular Plates subjected to Air and Underwater Blasts

International audienceThis paper presents a simplified analytical formulation that uses Lagrangian Energy Approach to predict air and underwater blast response of air-backed simply-supported circular steel plates. Triangular and exponential pressure profiles are considered for air and underwater blast loading respectively. Calculation of the response is divided into two stages. In the first stage, maximum impulsive velocity is determined by assum-ing that the plate has negligible deformation and then by using the conservation of linear momentum for air blast and Taylor’s one-dimensional analytical model for underwater blast. In the second stage of calculation, elastic deformation is obtained by applying the initial conditions determined from the first stage, also taking into account the rotatory inertia and water-added inertia effect. The obtained analytical solutions are tested with various plate aspect ratios as well as various loading levels and the results are compared with those from non-linear finite element explicit simulations. It is found that the proposed formulations correlate well with the finite element results giving only 5–20% discrepancy provided that the plate deflections are supposed to remain small compared to its thickness. Finally, the advantages and limitations of the present method are discussed

Seroprevalence and associated risk factors of Toxoplasma gondii infection among slaughterhouse workers in Yangon Region, Myanmar: A cross-sectional study

Background Toxoplasmosis, having the significant consequences affecting mortality and quality of life, is still prevalent in various places throughout the world. The major gap in surveillance for Toxoplasma gondii infection among high-risk population, slaughterhouse workers, is an obstacle for the effective policies formulation to reduce the burden of toxoplasmosis in Myanmar. Therefore, this study aimed to assess the seroprevalence of toxoplasmosis and associated factors of seropositivity among slaughterhouse workers in Yangon Region, Myanmar. Methods A cross-sectional study that was conducted from June to November 2020 included 139 slaughterhouse workers involving at five main slaughterhouses under Yangon City Development Committee, Myanmar. The presence of IgG and IgM anti-T. gondii antibodies in serum was detected using the OnSite Toxo IgG/IgM Combo Rapid Test. A face-to-face interview was also performed using pretested structured questionnaires to obtain the detail histories: sociodemographic characteristics, level of knowledge, occupational factors, and environmental factors related to T. gondii infection. Bivariate logistic regression was used to determine the factors associated with T. gondii infection. Results Of all participants, the overall seroprevalence of anti-T. gondii was 43.9% (95% CI: 35.5–52.5%), of whom 98.4% (95% CI: 91.2–100.0%) were reactive only for IgG antibody and 1.6% (95% CI: 0.0–8.8%) were reactive for IgG and IgM antibodies. The significant factors associated with the seropositivity of T. gondii antibodies were blood transfusion history (OR: 5.74, 95% CI: 1.17–28.09), low level of knowledge (OR: 2.91, 95% CI: 1.46–5.83), contact with animal organs, muscles or blood (OR: 14.29, 95% CI: 1.83–111.51), and animals most frequently slaughtered (cattle) (OR: 3.22, 95% CI: 1.16–8.93). Conclusions A high seroprevalence of toxoplasmosis was detected among slaughterhouse workers in Yangon Region and it raises a significant public health concern. Therefore, providing health education regarding toxoplasmosis, enforcement of personal hygiene practices in workplaces, the establishment of training for occupational hygiene, and commencement of the risk assessment and serological screening for toxoplasmosis are crucial to curtail the prevalence of T. gondii infection among slaughterhouse workers