scholarly journals Fatigue Failure of a Pressing Machine

2021 ◽  
Vol 11 (1) ◽  
pp. 398
Author(s):  
Martin Garan ◽  
Vladimír Chmelko ◽  
Miroslav Šulko ◽  
Miloš Musil
Keyword(s):  
Finite Element Method ◽  
Cross Section ◽  
Notch Root ◽  
Methodological Approach ◽  
Notch Effect ◽  
Critical Cross Section ◽  
Statistical Interpretation ◽  
Direct Measurements ◽  
The Press ◽  
Method Model

This article presents an analysis of the causes of a fatigue crack in the guide bar of a pressing device. The detailed analysis included the analysis of a material’s microstructure and its cyclic properties. Direct measurements of the strains during operation allowed the nominal loading process in the critical cross-section of the press subassembly to be obtained. The notch effect of the inner thread of the guide bar was analyzed using a precision FEM (finite element method) model and was followed by the transformation of the nominal loading into the notch root. A methodological approach was formulated based on the analyses made, which lay in the statistical interpretation of the factors leading to an identification of the cause of an early fracture.

Backscattering Analysis of Cylinder Shaped Scatterer in Vegetation Medium: Comparison Between Theories

2020 ◽  
Vol 2 (1) ◽  
pp. 15-18
Author(s):  
Syabeela Syahali ◽  
Ewe Hong Tat ◽  
Gobi Vetharatnam ◽  
Li-Jun Jiang ◽  
Hamsalekha A Kumaresan
Keyword(s):  
Numerical Solution ◽  
Cross Section ◽  
Traditional Method ◽  
Microwave Remote Sensing ◽  
Solution Model ◽  
Complex Nature ◽  
Good Match ◽  
Equivalent Source ◽  
Backscattering Cross Section ◽  
Method Model

This paper analyses the backscattering cross section of a cylinder both using traditional method model and a new numerical solution model, namely Relaxed Hierarchical Equivalent Source Algorithm (RHESA). The purpose of this study is to investigate the prospect of incorporating numerical solution model into volume scattering calculation, to be applied into microwave remote sensing in vegetation area. Results show a good match, suggesting that RHESA may be suitable to be used to model the more complex nature of vegetation medium.

Numerical simulations of temperature fields in the uncooled nozzle of a short-range anti-aircraft rocket engine with an insert in the critical section made of various materials

2021 ◽  
Vol 70 (1) ◽  
pp. 15-30
Author(s):  
Mateusz Zieliński ◽  
Piotr Koniorczyk ◽  
Janusz Zmywaczyk ◽  
Marek Preiskorn
Keyword(s):  
Numerical Simulations ◽  
Cross Section ◽  
Heat Flux Density ◽  
Short Range ◽  
Rocket Engine ◽  
Transient Heat Conduction ◽  
Critical Section ◽  
Temperature Fields ◽  
Critical Cross Section ◽  
Calculation Results

Abstract. The paper presents numerical simulations of transient heat conduction in the uncooled nozzle of a short-range anti-aircraft rocket engine. The calculations were made for the configuration of the nozzle with an insert in the critical section made of various materials. The inserts used were: POCO graphite, Al2O3 ceramics, ZrO2-3Y2O3 ceramics. For comparison, numerical simulations of the heat transfer in a nozzle made entirely of St 45 steel, the melting point of which is 1700K, were also carried out. The engine's working time was in the order of 3 s. Numerical simulations were performed using the COMSOL program. The calculation results are given in the form of temperature dependence and heat flux density as a function of time in the critical cross-section. Keywords: non-cooled nozzle, rocket engine, temperature field

The Use of Strain Energy and Fracture Correlation to Determine Life Expectancy for Notched Components

2009 ◽  
Author(s):  
Onome Scott-Emuakpor ◽  
Tommy George ◽  
Charles Cross ◽  
M.-H. Herman Shen
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Cross Section ◽  
Strain Energy ◽  
Notch Root ◽  
Stress Gradient ◽  
Strain Curve ◽  
Experimental Results ◽  
Cyclic Process ◽  
Notched Components

An energy-based method for predicting fatigue life of half-circle notched specimens, based on the nominal applied stress amplitude, has been developed. This developed method is based on the understanding that the total strain energy dissipated during a monotonic fracture and a cyclic process is the same material property, where the density of each can be determined by measuring the area underneath the monotonic true stress-strain curve and measuring the sum of the area within each Hysteresis loop in the cyclic process, respectively. Using this understanding, the criterion for determining fatigue life prediction of half-circle notched components is constructed by incorporating the stress gradient effect through the notch root cross-section. Though fatigue at a notch root is a local phenomenon, evaluation of the stress gradient through the notch root cross-section is essential for incorporating this method into finite element analysis minimum potential energy process. The validation of this method was carried out by comparison with both notched and unnnotched experimental fatigue life of Aluminum 6061-T6 (Al 6061-T6) specimens under tension/compression loading at the theoretical notch fatigue stress concentration factor of 1.75. The comparison initially showed a slight deviation between prediction and experimental results. This led to the analysis of strain energy density per cycle up to failure, and an improved Hysteresis representation for the energy-based prediction analysis. With the newly developed Hysteresis representation, the energy-based prediction comparison shows encouraging agreement with unnotched experimental results and a theoretical notch stress concentration value.

DYNAMIC SIMULATION OF THE TAILING PROCESS IN HOT FINISHING MILL

2008 ◽  
Vol 22 (31n32) ◽  
pp. 5661-5666
Author(s):  
SHINIL KIM ◽  
CHENG LU ◽  
XIAOZHONG DU ◽  
ANH KIET TIEU
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Tensile Stress ◽  
Deformation Behavior ◽  
Speed Ratio ◽  
Roll Speed ◽  
Dynamic Finite Element ◽  
Finishing Mill ◽  
Explicit Dynamic ◽  
Method Model

In this paper an explicit dynamic finite element method model has been developed to investigate the strip deformation behavior between two adjacent stands in hot finishing mill. The effect of the roll speed ratio of second stand to first stand on tension and the tailing behavior of the strip has been discussed in details. It has been found that the strip accumulation occurs if the roll speed ratio is small. The tensile stress increases with the roll speed ratio. During the tailing process the accumulated strip caused by the small roll speed ratios knocks onto the roll, while the swing of the strip tail occurs for the large roll speed ratios and it strikes the roll as well. Both tailing phenomena will result in the strip tail pincher or roll damage in the real operation.

Obtaining the thermal resistance of air enclosed at the interface of multilayer fabrics by simulation

2018 ◽  
Vol 89 (15) ◽  
pp. 3178-3188 ◽  
Author(s):  
Hua Shen ◽  
Lexi Tu ◽  
Xiaofei Yan ◽  
Sachiko Sukigara
Keyword(s):  
Finite Element Method ◽  
Surface Roughness ◽  
Thermal Resistance ◽  
Three Dimensional ◽  
Estimating Equation ◽  
Experimental Result ◽  
Dimensional Finite Element ◽  
Experimental Values ◽  
Three Dimensional Finite Element ◽  
Method Model

An air layer enclosed at the interface was largely responsible for the insulation results of multilayer fabrics obtained from experiments. In this study, a three-dimensional finite element method model, in which the air layer enclosed at the interface of multilayer fabrics was ignored, was developed to calculate the fabric thermal resistance, and the result obtained from the fabric model was independent of the air. A Thermolab II Tester KES-F7 was also used to measure the thermal resistance of fabrics, and the experimental results were influenced by the air layer. By comparing the simulation and experimental result, the air layer thermal resistance was determined, and then an estimating equation, which can be used to estimate the fabric and air layer thermal resistance for multilayer fabrics, was proposed. The results suggested that the surface roughness of fabrics was strongly related to the air layer thermal resistance, with a linear relationship between them. Moreover, for multiple layers stacked by different fabrics, the air layer thermal resistance at the interface was mainly decided by the fabric with the rougher surface. An estimating equation was also developed to predict the thermal resistance of multilayer fabrics and good correlation between predicted and experimental values was observed.

scholarly journals Assessment of Rectangular Cavity in Concrete Gravity Retaining Wall using Finite Element Method

2019 ◽  
Vol 8 (4) ◽  
pp. 2656-2661
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Distribution ◽  
Cross Section ◽  
Retaining Wall ◽  
Rectangular Cavity ◽  
Gravity Retaining Wall ◽  
The Cross ◽  
Conditions Of Stability ◽  
Element Method

The design of the Gravity retaining wall (GRW) is a trial and error process. Prevailing conditions of backfill are used to determine the profile of GRW, which proceeds with the selection of provisional dimensions. The optimum section is having factors of safety of stability higher than the allowable values and stresses in the cross-section smaller than permissible. The cross-section is designed to fulfill conditions of stability, subjected to very low stresses. The strength of the material, which is provided in the cross-section remains unutilized. A computer program is developed to find stresses at various locations on the cross-section of GRW using the Finite Element Method (FEM). A discontinuity in the form of a rectangular cavity is introduced in the cross-section of GRW to optimize it. The rectangular cavity is introduced in the cross-section of GRW at different locations. An attempt is made in this paper to find the stress distribution in the gravity retaining wall cross-section and to study the effect of the rectangular cavity on the stress distribution. Two cases representing different locations are considered to study the effect of the cavity. The location of the cavity is distinguished by the parameter w, the effects of cases with varied was 0.2305 (Case-I) and 0.1385 (Case-II) are observed. The cavity, which is provided not only makes the wall structurally efficient but also economically feasible.

scholarly journals Analysis of Timoshenko beam with Koch snowflake cross-section and variable properties in different boundary conditions using finite element method

2021 ◽  
Vol 13 (11) ◽  
pp. 168781402110609
Author(s):  
Hossein Talebi Rostami ◽  
Maryam Fallah Najafabadi ◽  
Davood Domiri Ganji
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Boundary Conditions ◽  
Natural Frequency ◽  
Cross Section ◽  
Timoshenko Beam ◽  
Natural Frequencies ◽  
Variable Properties ◽  
The Third ◽  
Koch Snowflake

This study analyzed a Timoshenko beam with Koch snowflake cross-section in different boundary conditions and for variable properties. The equation of motion was solved by the finite element method and verified by Solidworks simulation in a way that the maximum error was about 2.9% for natural frequencies. Displacement and natural frequency for each case presented and compared to other cases. Significant research achievements illustrate that if we change the Koch snowflake cross-section of the beam from the first iteration to the second, the area and moment of inertia will increase, and we have a 5.2% rise in the first natural frequency. Similarly, by changing the cross-section from the second iteration to the third, a 10.2% growth is observed. Also, the hollow cross-section is considered, which can enlarge the natural frequency by about 26.37% compared to a solid one. Moreover, all the clamped-clamped, hinged-hinged, clamped-free, and free-free boundary conditions have the highest natural frequency for the Timoshenko beam with the third iteration of the Koch snowflake cross-section in solid mode. Finally, examining important physical parameters demonstrates that variable density from a minimum value to the standard value along the beam increases the natural frequencies, while variable elastic modulus decreases it.

scholarly journals Modeling of crack opening mode sif for a crack in a thin-walled structural channel beam

2021 ◽  
Vol 102 (2) ◽  
pp. 78-86
Author(s):  
Mykola Pidgurskyi ◽  
Mykola Stashkiv ◽  
Ivan Pidgurskyi
Keyword(s):  
Finite Element Method ◽  
Cross Section ◽  
Simulation Modeling ◽  
Crack Opening ◽  
Intensity Factors ◽  
Inertia Moment ◽  
Structural Channel ◽  
Opening Mode ◽  
Thin Walled ◽  
Channel Beam

The analysis of engineering methods for determining stress intensity factors (SIF) for defective elements of open profile (channels) under bending is carried out. Mathematical models are created and dependences for calculation of SIF are deduced using two methods: using nominal stresses in net-section and using change of the inertia-moment of the profile cross-section. The obtained results are compared with the data of SIF for the crack in the channel obtained during simulation modeling using finite element method.

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