Papers by Keyword: Fatigue Analysis

Abstract: Reinforced concrete dapped end beams (RC-DEBs) in service suffer damage near the reentrant section under unknown loading conditions, reducing service life, particularly when recurrent loading is considered. In this investigation, a Finite Element Model (FEM) of a standard RC-DEB was used, together with a 3-dimensional concrete model and a fixed constitutive model. The girder reinforcement was designed in compliance with Eurocode 2 (EN-2) criteria for shear and deflection analysis. The level of deterioration under fatigue difficulties was determined by doing a fatigue analysis of moving and fixed pulsing loads at the midpoint and offset loading. A scaled-down experimental validation of the FEM for fixed pulsing loading was considered to better understand fatigue deterioration for practical applications. The major mode of damage observed is shear brittle failure at the beam's reentrant region. Although the moving load proved to be more damaging than the fixed pulsing load, loading at an offset of a/d of unity had an effect on the reentrant portion. The EN-2 code is nonconservative when it comes to describing the reinforcement at the reentrant section; for optimal performance, the hanger reinforcement must be properly anchored to the shear.

Abstract: Super Austenitic Stainless Steels (SASS) belongs to the category of austenitic stainless steels which were known for their excellent corrosion resistance when used in structural applications like desalination plants, oil piping systems, heat exchanger equipments which demands high temperature service and harsh environments. Several works on SASS dealt about the corrosion resistance of the material in its normal base metal form. But structural uses needs SASS to be welded with similar or dissimilar materials to fit into the applications. This study aims to present a detailed view on issues related to the weldability of super austenitic stainless steels and the future scope of welding on SASS.

Abstract: The objective of this review article is to review literature on fatigue analysis and biomaterials studies in Endodontics. The nitinol and gutta-percha are widely used biomaterials in the Endodontic fields. The nitinol is used to manufacture the Endodontic files which are used for preparation of the root canal. The preparation of the root canal consist of removal of dead tissue, substrates and debris from the decayed root canal. During the preparation of root canal shaping of the root canal is done to develop the perfectly prepared cavity. The gutta-percha is used to fill the prepared cavity. The nitinol and gutta-percha are important contributing biomaterial for success of root canal treatment. This review article has been reviewed contemporary studies on nitinol and gutta-percha biomaterials. For the success of root canal treatment the fatigue of Endodontic file and three dimensional filling of root canal are two important aspect. The Endodontic files during the cleaning and shaping of the canal gets subjected to torsion fatigue failure or cyclic fatigue failure. The past studies lacks the exact knowledge about these failures as well as analysis approaches to be followed for correct diagnosis. This review article helps to overcome this difficulties. Moreover, the fatigue factors are discussed so that researcher can get little idea about failure point of the nitinol rotary files. The review consist of A contemporary review of nitinol alloy studies, A review of fatigue failure diagnosis, A contemporary review of gutta-percha quality assessment techniques studies, A novel approach for fatigue analysis of nitinol file and A novel approach for quality assessment of gutta-percha etc.

Abstract: Pressurizer surge line is one of the key equipments of nuclear power plants. The thermal stratification due to the intersection of hot and cold fluids inside the pressurizer surge line may affect the safe operation of nuclear power plant. In order to investigate the stress distribution and fatigue characteristics of surge line subjected to long-term thermal stratified loadings, a mechanical model of the surge line was established. And then, according to different temperature distribution assumptions, thermal stress analysis and fatigue assessment were conducted. The results show that the maximum stress appears under the load condition with maximum temperature difference, and finer temperature distribution can obtain more accurate stress and displacement results. The maximum value of fatigue cumulative coefficient appears at the junction of straight pipe and elbow with large temperature difference.

Abstract: In this paper, the influence of friction on static, dynamic characteristics, the strength and lifetime of a 3-axes flexible CNC machine tool are taken into account. The machine tool is first modelled by using finite element method (FEM) to perform static structural analysis. After that, the dynamic effects caused by the inertia forces and the displacement of moving part of the machine on contact stress are considered in this study. Then, the stress and contact force distributions on solid-flexible contact are also obtained. Finally, the influence of dynamic structure, cutting conditions and material properties on strength and lifetime of CNC machine tool are discussed by using fatigue analysis. Consequently, the proposed method can be used for efficient simulation of structural dynamics, lifetime assessment as well as interactions of the real CNC machine with the machine tool structure in a virtual environment.

Abstract: This paper presents the FEM approach of fatigue life estimation of a layered composite plate having a central elliptical cut-out subjected to time variation loads. Some properties and material data, such as data used for the S-N curve / Wöhler curve of the material, represented in cyclic stress versus number of cycles to failure coordinates, which is required for starting the fatigue analysis, were taken from the OPTIMAT database.The plate analysis was parameterized and modeled with the Shell281 element type. This type of element can be used in a triangular form more efficiently than other types of shell elements available in version 15 of ASYS APDL.Initially, the static analysis was performed to identify the node with the maximum principal stress (hot spots). This node was used for performing the fatigue analysis. The fatigue parameter to estimate fatigue life is cumulative fatigue usage factor. This factor is obtained by adding together all individual usage factors calculated for each variable load that is applied to the analyzed plate. The fatigue usage factor is used to estimate the percentage of life that is consumed after applying the fatigue loads. The value of the usage factor is in the range from 0 to 1.

Abstract: A plastic strain correction factor is used in a simplified elastic-plastic fatigue analysis of nuclear power plant components. Numerical investigation on the plastic strain correction factor is presented for the case of the primary and secondary stress range exceeding three times the design stress intensity value under thermal-mechanical loadings. The plastic strain correction factor was computed separately by following the RCC-M code and applying the elastic-plastic finite element analysis. The influence of loading ratio, loading controlled mode and ambient temperature on the plastic strain correction factor was discussed. It was shown that the plastic strain correction factor computed from the RCC-M code is not as conservative as that from the complete elastic-plastic finite element analysis when the primary plus secondary stress range is close to three times the design stress intensity value. However, it is too conservative when the primary plus secondary stress range is more than three times the design stress intensity value multiplying parameter m (use in RCC-M code). Additionally, a new formula of plastic strain correction factor was proposed to provide a complete envelope curve to the entire primary plus secondary stress range.

Abstract: In this paper, the purpose is to compare three different cone fit of dental implant around the surrounding bone tissue that influence on fatigue and biomechanics, it is also to provide a theoretical basis for the design and clinical application of dental implant. The method is that loading the force 100N and 200N with different angle to the three different cone with dental implant with the finite element analysis (FEA) that analyzes the stress and fatigue in ideal conditions. The Results is that when the loading is vertical, cone for 3 degrees of the implant have the best performance. The cone for 80 degrees of the implant is min among the max equivalent stress of the implants. However, comprehensive view, Cone for 24 degrees of the implant the most stable. we find that cone of different implant when subjected to the same force the maximum equivalent stress is different, smaller conical implant under vertical load force have good performance, but with the increase of the loading angle the bigger conical implant performance better.

Abstract: Multi-objective optimization method was adopted for obtaining appropriate dimensions of a new type of inner support in tire. Based on optimized inner support in tire with three monomer block components, finite element models were established by HyperMesh, and dynamic simulation on safety property was completed on LsDyna3D. For this type of inner support in tire, strength is enough during tire burst. After fatigue damage analysis, safety property of inner support after tire burst is well enough too. It is certain for the inner support to work well not only during tire burst but also after tire burst.

Abstract: EMU gearbox is a key component of high-speed train, the reliability of the gearbox will directly affect the operational safety of EMU. The box of EMU gearbox is with light alloy materials, bearing structure, so the box is subjected to greater loads and shock and vibration. Designers most take into account the static strength and stiffness of the box, ignore the fatigue failure. Fatigue failure is the leading cause of mechanical structural failure, while the peak load cycle fatigue failure is often far less than estimated in accordance with the static fracture analysis "safe" load, so the EMU gearbox box’s fatigue analysis is needed. Combining high-speed EMU gearbox actual operating conditions, using finite element method to do fatigue analysis of the gearbox box while the analysis result is evaluated and amended by the Smith schematic analysis method.