Numerical FEM Analysis Research Articles

Numerical research of thermal stress in a gas burner with a cylindrical mantle in relation to its construction

Over the last few years there has been a great interest in research into the improvement of gas condensing boilers with pre-mixing. Many researchers are concerned with the improvement of the construction of these boilers, whose individual parts directly affect some parameters such as combustion efficiency, burning intensity, flame stability and NOx emissions. The outer mantle of a cylindrical burner stands out among the parts of the structure as the said parameters depend on it This paper analyses the outer cylinder of the premixed burner in relation to thermal stress. Numerical FEM analysis was performed based on experimental measurements and CFD input data. The tests were carried out in different gas and different materials. The results obtained show different thermal stresses which are dependent on the different gas and materials on the outer cylindrical mantle. This indicates the necessity to optimize materials and patterns applied to the outer cylindrical mantle of the burner, which will be the subject of further research.

A Pulsed Thermal-Flow (PTF) Sensor Measures Velocity of Flow and Thermal Diffusivity

A prototype pulsed thermal-flow (PTF) sensor was designed, fabricated in micro-electro-mechanical system (MEMS) technology and tested on various gases. The objective of our development project was twofold: first, to realize a micro-sensor of low cost and ultra-low energy consumption that, secondly, accurately and rapidly measures gas flow velocities within a wide temperature range. The sensor of size 4.2 × 3.2 × 0.6 mm3 is of micro-beam type. It consists of one Joule heating element and several resistance thermometers at distinct distances from the heater. The heater is operated in a single short pulse mode of a fixed duration that can be chosen between 10 and 100 µs. Due to this ultra-short time of excitation, there is no natural convection during a run. For typical values of pulse width (30 µs) and heater power (6 mW), the energy per measurement is smaller than 0.2 µJ. Typically, the excess temperature of the heater is limited to 5 K. This relatively small overtemperature considerably reduces radiative heat transfers otherwise interfering with the process of measuring. The velocity of flow is determined by the time-of-flight technique of the imposed heat pulse as the tracer in a few milliseconds. The measurement uncertainty is preliminary assessed to be 1.5% within a range from 0 to 7 m/s. The working temperature may vary between − 100 and 300 °C. The sensor not only measures the velocity of flow but also the thermal diffusivity of the gas under test. The report provides a complete analytical model of the functional principle of the sensor, a numerical FEM analysis of the 2-dim. isotherms, the heat flow pattern of the active surface of the sensor and an empirical model to fit the temperature response of the thermometers. The latter one effectively supports the evaluation of the acquired data. Exemplary experimental results are presented for nitrogen, methane and the two gas binary mixtures 80CH4–20N2 and 80CH4–20H2. The results deviate from their analytically predicted values by at most ± 1%. To the best of our knowledge, the PTF-sensor operates at the lowest energy consumption known so far. This characteristic makes it the perfect flow sensor for battery-operated long-term flow velocity recording systems.

Numerical Analysis of Settlement of a Structure Situated on a Heterogeneous Loess Subsoil

The paper presents FEM numerical analyses of interaction of structures situated on loess subsoil. Static CPT tests on loesses from Lublin, Poland, was used in the process of defining subsoil variability. The calculations assumed a variant of weak soil under individual foundation footing. It was shown that variable stiffness of loess subsoil causes heterogeneous settlements of the building, which leads to deformations and affects internal forces within the structure.

Tibio talar contact stress: An experimental and numerical study

AimsTibio-talar contact stress has been evaluated and successively compared by performing an ankle contact finite element (FE) analysis and an experimental test carried on an assembled simple synthetic model of ankle equipped with a high-resolution (Tekscan) pressure sensor. MethodsA numerical FEM analysis was carried out by simulating the ankle joint (foot, and tibia) in order to investigating the stress shielding on the contact surfaces. The foot was constrained at the base while a load of 980 N was applied on the top of the tibia. The same setup was experimentally reproduced by introducing a high-resolution (Tekscan) pressure sensor between tibia and foot. ResultsResults evidenced a good agreement between numerical and experimental data, a percentage difference of 15% was evaluated on the equivalent Von Mises contact stress. ConclusionThe obtained results reveal interesting consequences deriving by taking into account how the stress shielding can influence the integrity and resistance of bones. The methods used for this validation enable formal comparison of computational and experimental results, and open the way for objective statistical measures of regional correlation between FE-computed contact stress distributions from comparison articular joint surfaces.

Design of Transverse Stiffeners in Plate Girders with Corrugated Web

This study reports investigations into the effect of relative flexural stiffness of intermediate stiffeners γ on the failure zone location in the corrugated web. The study also aimed at obtaining stiffness criterion for intermediate stiffeners that depends on the magnitude of the plate geometry parameter α. To achieve the goals of the study, experimental investigations were conducted into load displacement paths of four exemplary SIN girders. They were simply supported girders, made to full scale, and composed of pre-assembled units. The phenomena occurring in the experiment were represented using the Finite Element Method. For FEM numerical analysis of girders with intermediate stiffeners, models with the web height of 1000, 1250 and 1500 mm, made from 2; 2.5 and 3 mm thick corrugated sheet metal were used. Due to the analysis of 52 girder numerical models, it was possible to propose the stiffness criterion of intermediate stiffeners. The criterion was based on the assessment of shear buckling strength of the corrugated web. Using the regression method, dimensionless coefficients of the stiffener stiffness ks dependent on the optimum stiffness γ were determined. Based on estimated coefficients of the stiffener stiffness ks, the absolute minimum stiffness of intermediate stiffeners Ismin used in corrugated web plate girders was calculated. It was demonstrated that the use of an intermediate stiffener, the stiffness of which is greater than Ismin , additionally leads to a change in the location of the site of the web shear buckling.

Increasing the Seismic Resistance of Wood-frame Buildings by Applying PU Foam as Thermal Insulation

Wood-frame buildings are very common in regions that are exposed to earthquakes. Most of residential buildings are constructed using this technology; therefore, the seismic resistance of them is really essential in order to prevent human losses and structural damage. The aim of the present article is to show the results of the detailed numerical FEM analysis focused on the seismic behaviour of the wood-frame house with different in-wall insulation materials. The results of the study clearly indicate that using polyurethane (PU) foam instead of mineral wool leads to the increase in the rigidity of the structure and, therefore, to the substantial reduction in the structural response under different seismic excitations. The results also show that, generally speaking, the level of reduction in the displacement response increases with the increase in the magnitude of the earthquake, which even furthermore benefits the application of PU foam as an insulation material. It has also been concluded that the method of using PU foam can be successfully applied not only in the newly constructed wood-frame houses but also in existing ones since replacing the mineral wool with PU foam is relatively easy and not so much expensive.

FEM numerical analysis of the shape bow cross-section for the rigidity of the wheelset measuring device

FEM numerical analysis of the shape bow cross-section for the rigidity of the wheelset measuring device

Zastosowanie techniki wirtualnej i poszerzonej rzeczywistości do wizualizacji wyników analiz numerycznych MES

An innovative approach for presenting the results of numerical FEM analysis is presented. Proposed visualization method uses virtual and augmented reality techniques for this purpose. The practical application of the new tool is presented on the example of strength analysis of the side beam of the curtainsider semi-trailer.

Behavioural analysis of vertical and batter pile groups under vertical and lateral loading in sand

Laboratory model tests were carried out to study the behaviour of vertical piles and batter pile groups under vertical and lateral load. The model pile groups were made up of mild steel rod of 8-mm diameter. Parameters such as degree of batter and different length to diameter ratios of 7.50, 15.00 and 22.50 were considered in this study. The size of the model tank was 1000 mm × 1000mm × 800 mm. Experiments were performed on 3 × 3 model pile groups with a row of batter piles both positive and negative in addition to vertical pile groups with batter angle 0° in sandy soil subject to vertical and lateral loads. It was observed that the behaviour of vertical pile groups and group of piles with batter piles were similar but it showed substantial variation in the capacity of pile groups. Results indicated that the load–settlement relationships were non-linear for all model pile groups both under vertical and lateral loading. Numerical FEM analysis using ABAQUS/CAE 6.11 was also used to compare and validate the load carrying capacity of pile groups obtained from the experimental model tests.

Strain hardening polypropylene fiber reinforced composite from hydrated ladle slag and gypsum

The use of industrial by-products brings both economic and environmental benefits. Ladle slag (LS) from steel processes is a promising raw material and has been used as a precursor in a few studies. To better understand the benefits of LS mainly on mechanical behavior, in this investigation, an ettringite-based binder was produced from the hydration between LS and gypsum. The material was reinforced with 2% v/v high tenacity polypropylene (HTPP) fiber to attain a high performance fiber reinforced cementitious composite with pseudo strain hardening (PSH) behavior. In addition, results of FEM numerical analysis show the accurateness of an available constitutive model in predicting the mechanical response of the HTPP fiber reinforced hydrated LS composite. Additionally, the experimental results reveal that using HTPP fiber greatly enhanced the mechanical properties of the hydrated LS. Moreover, PSH behavior and eventually multiple fine cracks were recorded by the digital image correlation (DIC) technique under uniaxial tensile tests. The numerical simulations show the capability of the concrete damage plasticity (CDP) model to predict the nonlinear behavior of the material with a good agreement between experimental and numerical predictions.

Load monitoring of aircraft landing gears using fiber optic sensors

We report on the use of Fiber Bragg Grating (FBG) sensors integrated onto an aircraft landing gear for remote and real-time load monitoring. Several FBGs strain sensors, both in a linear and tri-axial configuration, have been integrated on different locations of true landing gears (both Main and Nose gears) based on their load condition derived from FEM numerical analysis and exposed to numerous qualification lab tests where the load applied to the gears was varied in the range 0–20 kN. To this aim, the gears were mounted on a 25kN hydraulic press, that changed the shock absorber route from 0 mm up to 200 mm (corresponding to the maximum take-off weight, ∼4600 kg). Obtained results are in good agreement with those provided by reference electrical strain gauges located very close to their optical counterparts, and demonstrate the great potentialities of FBG sensors technology to be employed for remote and real time load measurements on aircraft landing gears.

Shear Buckling of Plate Girders with Corrugated Web Restrained by End Stiffeners

The study reports the investigations into the effect produced by flexural stiffness of end stiffeners on the design buckling resistance of the sine wave webs of girders. Experimental investigations were concerned with load displacement paths in sinusoidally corrugated web girders, composed of structural items and made to the full scale . The phenomena occurring in experimental investigations were represented using the Finite Element Method. In numerical models based on FEM analysis, the same failure modes of webs that were found in experimental investigations into corrugated web girders were accounted for. FEM numerical analysis was performed for girder models with webs 500, 1000, 1250 and 1500 mm in height, made of corrugated sheet metal 2, 2.5 and 3 mm in thickness. On the basis of laboratory tests and FEM analysis, a new method for estimating design shear buckling resistance for girders with semirigid and rigid end stiffeners was proposed. The method relies on the determination of interactive buckling resistance. The solution presented in this study was compared with formulas currently used for buckling resistance estimation. It was shown that the use of girder rigid end stiffeners produces in increase in shear buckling resistance up to 11%. Conclusions were drawn and recommendations were made with respect to the sizing of sine wave corrugated web girders with semirigid and rigid end stiffeners.

Experimental measurement and FEM numerical analysis of vibration properties of CFRP laminates with flexible sheets inserted at interlaminars

Experimental measurement and FEM numerical analysis of vibration properties of CFRP laminates with flexible sheets inserted at interlaminars

FEM numerical analysis of the compaction of a mixture of brake pad components taking account of the real shapes and dimensions of particles

FEM numerical analysis of the compaction of a mixture of brake pad components taking account of the real shapes and dimensions of particles

Effects of honeycomb geometry on stress concentration due to defects

In this study, to investigate the effects of honeycomb geometry on stress concentration due to defects, a symmetric hexagonal honeycomb core was developed and this was followed by performing a series of FEM numerical studies on stress concentration due to defects under uniaxial and biaxial loading. The simulations indicated that the degree of the stress concentration in the front of the defect is influenced by the geometric shape of defects and is also sensitive to anisotropy due to the honeycomb geometry. Furthermore, a new technique is proposed in which honeycomb structures with defects are replaced by orthotropic plates with an elliptical hole to evaluate the stress concentration. The validity of the approximation method is verified by the results of the numerical FEM analysis.

Collapse mechanisms of masonry arches with settled springing

Over last centuries, masonry arch has been one of the most used basic structural systems in buildings and infrastructures. One of the most interesting current issues relates safety assessment of existing built heritage, which is often subject to deterioration phenomena. For such reasons, this work aims at analyzing the applicability of classical limit analysis for investigating the safety of masonry arches subject to springing settlements. An extensive parametric analysis is performed considering different geometrical configurations and settlement directions. Then, analytical predictions are compared with results from experimental tests and FEM numerical analyses. Such results confirm the reliability of limit analysis when dealing with the safety assessment of settled masonry arches.

Experimental and Numerical Analysis of Compression Thin-Walled Composite Plates Weakened by Cut-Outs

Abstract Buckling and postbuckling response of thin-walled composite plates investigated experimentally and determinated analytically and numerically is compared. Real dimension specimens of composite plates weakened by cut-out subjected to uniform compression in laboratory buckling tests have been modelled in the finite element method and examined analytically based on P-w2 and P-w3 methods. All results were obtained during the experimental investigations and the numerical FEM analysis of a thin-walled composite plate made of a carbon–epoxy laminate with a symmetrical eight-layer arrangement of [90/-45/45/0]s. The instrument used for this purpose was a numerical ABAQUS® program.

High Aspect Ratio Thin Rib Shape Processing of Carbon Material for Electrical Discharge Machining Molds

Aluminum alloy die casting products are used for automotive LED lamp installation parts. The high aspect ratio shape used for large-volume heat problems needs thin rib parts. In the present study, we obtained basic data for the development of long axis type end mill tools for electrical discharge machining carbon material processing. At the same time, to evaluate the prototype development work, a special tool that enables high aspect ratio thin rib geometry processing was used. Longitudinal direction traverse cutting was done with a small diameter ball end mill tool in the carbon material for electrical discharge machining mold. The transfer accuracy and pick feed shape in the finished surface, the cutting resistance force, and the cutting edge shapes were examined to clarify the relationship between the cutting conditions set. Prototype development of the small-diameter end mill tool with a high rigidity, long axis was done using FEM numerical analysis method. The results showed that the small-diameter ball end mill tool with a tapered length axis in the prototype development had transfer accuracy of the cutting edge shape, and it was possible to reduce the finished surface roughness. Factors such as differences in tool shape are considered to greatly affect the tool rigidity.

AN ESTIMATING METHOD FOR LATERAL BEHAVIOR OF PILED-RAFT FOUNDATION

Some simplified design methods were proposed to predict behavior of lateral loaded piled-raft foundations on homogenous soil. One of them is the cone model method. However, only one average solution of pile behavior can be given by this method. It can’t evaluate the location factors of piles. Therefore, this paper describes a new simplified method to predict behavior of lateral loaded piled raft foundations covering the location factor of piles. At first, ground surface displacement is derived theoretically by Cerutti’s solution, then assuming that the raft foundation has rigid stiffness, these displacements are the same to calculation lateral loading distribution. Second, the ground displacement where pile placed could be estimated under calculated lateral loading. Third, the piles behavior are evaluated based on these lateral ground displacements. In addition, 3-D FEM numerical analysis were performed to compared with these solutions.

The TVT Glass Pavilion: Theoretical Study on a Highly Transparent Building Made with Long-Spanned TVT Portals Braced with Hybrid Glass-Steel Panels

In contemporary buildings, the architectural demand for a complete dematerialisation of load bearing structures can be satisfied only in limited cases with the exclusive structural use of glass. Otherwise, for challenging applications such as long spanned or high-rise structures, the use of hybrid glass-steel systems is mandatory. Glass, fragile but highly compressive resistant, is associated with steel, ductile and tensile resistant. The present research shows the feasibility study for a fully glazed pavilion made of six TVT (Travi Vitree Tensegrity) portal frames longitudinally braced by pre-stressed hybrid glass panels. The frames are about 20 m in span and 8 m in height. Appropriate multiscalar FEM numerical analyses, calibrated on the collapse tests performed on previous TVT large-scale prototypes, stated that the structural performance would be able to withstand heavy static and dynamic loads and stated the observance of the Fail-Safe Design principles.