Stress analysis of periodic notches by using the strain energy density approach

This research focuses on the stress analysis of periodic notches by using the strain energy density approach. Bolts, screws and rotary-shouldered connections, as examples of periodic notched components, play an important role in the performance of the machinery. The contents are related to two-dimensional (2D), as well as three-dimensional (3D) modeling of periodic notches both in the case of round and sharp notches. The analyses are based on the numerical modeling of periodic notches with linear elastic assumption of the material. The simple analytical expressions for the notch stress intensity factors (NSIFs) of periodic sharp notches, as well as theoretical stress concentration factors (SCFs) of periodic blunt notches are obtained. Using the strain energy density (SED) approach, the coarse mesh in the finite element models is used and compared with the results obtained from the fine meshing. In fact, using SED approach, the averaged strain energy in a control volume allows using the coarse meshes in order to determine the NSIFs and SCFs of notched components precisely. In the case of 3D analysis, the thickness effects with particular attention on coupling modes, which due to Poisson effect are automatically generated, are studied. These modes can have a significant effect on the structural integrity of mechanical components. In addition, two collaborative industry projects with: Officine Meccaniche Zanetti s.r.l. and Omera s.r.l. are successfully implemented

Auto generation of the center of gravity of tubular structures during crush deformation

Displacement of the center of gravity (COG) of tubular structures with various polygonal cross-sections is numerically investigated under an axial crush using the program code of ANSYS/LS-DYNA. A subroutine is developed using this code to calculate the COG of the deformed shape, during and after the crush. The effect of wall thickness on displacement of the COG is also investigated. Displacement of the COG decreases as the number of edges increases; it is a reasonable symmetric-deformed shape for the number of edges beyond eight. An even number of edges leads to a more symmetric displacement of the COG. The effect of the number of polygonal edges on symmetric deformation of the COG becomes more prominent as the initial wall thickness decreases. The higher number of edges stabilizes the deformed shape and the value of the mass moment of inertia of the deformed shape about the y axis (Iyy). The value of the mass moment of inertia about the x-z axes (Ixz) in comparison with I yy can be neglected in the case of dealing with an axial crush along the y direction

Auto adjust masses of automotive structures with desired centre of gravity

In this study a subroutine was developed and added in the pre-processing module of the frame work of commercial package of ANSYS to distribute the extra masses according to specific assigned centre of gravity (COG). The work further calculate the first bending and torsional natural frequencies of the simplified body in white (BIW) model of automotive in order to maximize these frequencies with final mass constraint. It is found that adding the extra masses symmetrically about longitudinal axis helps to improve the first bending and torsion natural frequencies. However, removing the mass along this axis leads to have higher values in the case of first bending and natural frequencies

Durability simulation of elastomeric materials using finite element method (FEM)

The paper presents a simulation work conducted on the elastomer subjected to cyclic loads. A 3D finite element model of elastomer specimen, in accordance to ASTM D412, was developed using CATIA and ANSYS commercial finite element (FEM) packages. Fatigue life predicted from the simulation was compared with well-documented published data and it showed an acceptable agreement. Meanwhile, the simulated strain-life results are slightly lower than the experimental data. Several factors which potentially influenced the variations of the results were noted. Finally, some recommendations are offered at the end of this study to further improve the simulation

Stress analysis of periodic notches by using the strain energy density approach

This research focuses on the stress analysis of periodic notches by using the strain energy density approach. Bolts, screws and rotary-shouldered connections, as examples of periodic notched components, play an important role in the performance of the machinery. The contents are related to two-dimensional (2D), as well as three-dimensional (3D) modeling of periodic notches both in the case of round and sharp notches. The analyses are based on the numerical modeling of periodic notches with linear elastic assumption of the material. The simple analytical expressions for the notch stress intensity factors (NSIFs) of periodic sharp notches, as well as theoretical stress concentration factors (SCFs) of periodic blunt notches are obtained. Using the strain energy density (SED) approach, the coarse mesh in the finite element models is used and compared with the results obtained from the fine meshing. In fact, using SED approach, the averaged strain energy in a control volume allows using the coarse meshes in order to determine the NSIFs and SCFs of notched components precisely. In the case of 3D analysis, the thickness effects with particular attention on coupling modes, which due to Poisson effect are automatically generated, are studied. These modes can have a significant effect on the structural integrity of mechanical components. In addition, two collaborative industry projects with: Officine Meccaniche Zanetti s.r.l. and Omera s.r.l. are successfully implemented.Questa ricerca si concentra su "Analisi delle sollecitazioni di intagliati periodici utilizzando l'approccio di densità di energia di deformazione", si è occupato di problematiche relative alla modellazione bidimensionale e tridimensionale di intagli periodici raccordati e a spigolo vivo. Bulloni, viti e connessioni rotanti spalle, come esempi di componenti intagliati periodiche, svolgono un ruolo importante nelle performance delle macchine. L'attività ha coinvolto prevalentemente la modellazione numerica in campo elastico ed ha permesso di ottenere delle semplici espressioni per la stima dei fattori d’intensificazione delle tensioni (NSIFs) e dei fattori teorici di concentrazione delle tensioni (SCFs) in funzione di tutti i parametri geometrici considerati. Le analisi numeriche sono state effettuate in prima battuta con mesh fitte e successivamente con mesh molto rade. Nel secondo caso l’energia di deformazione mediata in un volume di controllo ha permesso di determinare con precisione i fattori tensionali di riferimento e alcune espressioni per l’applicazione diretta a problematiche simili. Nel caso tridimensionale sono stati studiati e analizzati gli effetti legati allo spessore con particolare riferimento ai modi accoppiati che vengono automaticamente generati per effetto Poisson e che possono incidere in modo rilevante sull’integrità strutturale di componenti meccanici. I risultati raggiunti sono stati applicati a casi aziendali con due collaborazioni tutt’ora in atto con Officine Meccaniche Zanetti e Omera formalizzate in progetti di ricerca in cui il dottorando è stato il principale protagonista

Crash deformation simulation of tubular structure to determine automotive centre of gravity

In this study, the effects of crush behaviour of tubular structures have been investigated throughout simulation work. The axial crush was performed to predict the behaviour of tubular structures in terms of displacement of centre of gravity (COG) and mass moments of inertia (lyy and lxz ). Crush simulation includes two sections; close and open cross-sections respectively. In the case of close cross-sections, a displacement of COG of tubular structures with various polygonal cross-sections is numerically investigated under axial crush using program code of ANSYS/LS-DYNA. A subroutine is developed using this code to calculate the COG of deformed shape, during and after crush condition. The effect of wall thickness on displacement of COG is also investigated. Subsequently, a procedure to find real time COG of tubular structure during and after crush is developed. Base on this procedure, a macro is added in the frame work of ANSYS/LS-DYNA to study the deformation behaviour of tubular structure by the accurate criteria of COG,xxxx . Furthermore, the optimum number of edge of polygonal cross-section to have a reasonable symmetric deformed shape during crush is determined. It is found that the effect of number of polygonal edges on symmetric deformation of COG becomes more prominent as wall thickness of tubular structure decreases. The higher number of edges stabilizes the deformation shape. To examine the open cross-sections, the tubular structures with various Cee-shaped cross sections are numerically investigated. The subroutine used for the first section is performed again. Yet, the effect of wall thickness was also studied. Subsequently, the effect of opening angle of Cee becomes more prominent as the wall thickness of the structure decreases. As the thickness increases, displacement of the COG in crush direction almost stabilizes for all opening angle of Cee in the range of 100 − 900 degrees. Furthermore, variation of lyy of structure with thicker wall for different cases of applied mass is approximately identical. As a contribution to real application, Cee-shaped cross-sections with higher wall thicknesses can be used in the form of frame structures in automotive industry in order to reduce the overall weight of the structure and therefore, to save more energy. The study is the continue by incorporating a developed subroutine that added in the pre-processing module, in the frame work of ANSYS, distribution of the extra mass according to specific assigned COG and calculation the first bending and torsional natural frequencies of the simplified model in order to maximize these frequencies with final mass constraint was successfully investigated. It was found that adding the extra mass symmetrically about longitudinal axes of Body In White (BIW), higher values for first bending and torsional natural frequency is achieved

Durability simulation of elastomeric materials using finite element method (FEM)

The paper presents the simulation work on the elastomer subjected to cyclic loads. A 3D finite element model of elastomer specimen which in accordance with ASTM D412 was developed using CATIA and ANSYS commercial finite element (FEM) packages. The fatigue life predicted from simulation was compared with a well documented published data and show acceptable agreement. The simulated strain-life results are slightly lower than the experimental data. Several factors that potentially influenced the variation of the results were noted. Finally, some recommendations have been made at the end of this study to further improve the simulation

Durability simulation of elastomeric materials using finite element method (FEM)

The paper presents the simulation work on the elastomer subjected to cyclic loads. A 3D finite element model of elastomer specimen which in accordance with ASTM D412 was developed using CATIA and ANSYS commercial finite element (FEM) packages. The fatigue life predicted from simulation was compared with a well documented published data and show acceptable agreement. The simulated strain-life results are slightly lower than the experimental data. Several factors that potentially influenced the variation of the results were noted. Finally, some recommendations have been made at the end of this study to further improve the simulation