Innovative Teaching Approach Based on Finite Element Technique in Material Mechanics for Vocational Education

This paper proposed an innovative teaching approach based on finite element technique(FET)to improve the understanding of material mechanics.A teaching experiment was conducted using pure bending deformation of a beam as an example,and the deformation and stress distribution of the beam were analyzed using FET.The results showed that using color stress nephograms and color U nephograms can improve students’learning outcomes in mechanics classroom.The high levels of satisfaction and interest in incorporating new techniques into the classroom suggest that there is a need to explore and develop innovative teaching methods in mechanics and related fields.This approach may inspire educators to develop more effective ways of teaching material mechanics,and our research can contribute to the advancement of mechanics education.

Arc-length technique for nonlinear finite element analysis

Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.

APPLICATION OF TREFFTZ BEM TO ANTI-PLANE PIEZOELECTRIC PROBLEM

Anti-plane electroelastic problems are studied by the Trefftz boundary element method （BEM） in this paper. The Trefftz BEM is based on a weighted residual formulation and indirect boundary approach. In particular the point-collocation and Galerkin techniques, in which the basic unknowns are the retained expansion coefficients in the system of complete equations, are considered. Furthermore, special Trefftz functions and auxiliary functions which satisfy exactly the specified boundary conditions along the slit boundaries are also used to derive a special purpose element with local defects. The path-independent integral is evaluated at the tip of a crack to determine the energy release rate for a mode Ⅲ fracture problem. In final, the accuracy and efficiency of the Trefftz boundary element method are illustrated by an example and the comparison is made with other methods.

STRESS RATE INTEGRAL EQUATIONS OF ELASTOPLASTICITY

The stress rate integral equations of elastoplasticity are deduced based on Ref. [1] by consistent methods. The point at which the stresses and/or displacements are calculated can be in the body or on the boundary, and in the plastic region or elastic one. The existence of the principal value integral in the plastic region is demonstrated strictly, and the theoretical basis is presented for the paticular solution method by unit initial stress fields. In the present method, programming is easy and general, and the numerical results are excellent.

BRITTLE-DAMAGE ANALYSIS OF CRACKS UNDER CONDITIONS OF PLANE-STRAIN TENSILE LOADING

An abrupt damage model, taking full account of finite geometry changes, is used to study both the shapes of damage zones and the stress strain fields for a plane-strain tensile crack under the small-scale yielding condition. Two typical crack-tip damage profiles are simulated by the element vanish technique. The fracture toughness increment due to damage dissipation is evaluated in terms of the energy release rate.

A Two-Dimensional Mathematical Model to Analyze Thermal Variations in Skin and Subcutaneous Tissue Region of Human Limb during Surgical Wound Healing

During wound healing, the metabolic activity associated with each phase must occur in the proper sequence, at a specific time, and continue for a specific duration at an optimal intensity. Any disturbance in appropriate thermal environment may complicate the wound healing process and may give rise to wound infection. In the presented paper a transient state two-dimensional mathematical model has been developed to analyse thermal variations in skin and subcutaneous tissue (SST) region of human limb. Due to circular shape of human limb, model has been developed in polar coordinates. The domain of the study consists of two types of tissues: abnormal tissues and normal tissues. The post surgery peripheral tissue of human limb during healing time is considered as abnormal tissues. The effect of variable density of blood vessels in dermal layer of both tissues on the physical and physiological parameters is incorporated in the model. The effect of healing on physiological parameters of abnormal tissue is incorporated by considering the physiological parameters to be function of time “t”. The effect of different climatic conditions is considered in the model. Taking into account the variable core temperature due to anatomy of arteries and variable physiological parameters in dermal layer of peripheral region, the well known Pennes’ bio heat equation is used to analyse the time-dependent temperature distribution of both normal and abnormal tissues. Comparison between temperature profiles of both normal and abnormal tissue has been done using finite element approach with bilinear shape functions in polar coordinates. A computer program in MATLAB has been developed to simulate the results.

Holistic Approaches for Renovation of Large Housing Areas in Japan

Social imbalance and obsolescence of the built environment has emerged in large sized housing estates in metropolises. In particular, the requirement of such planned housing areas has not matched public service provided by the infrastructure. On not only physical but also social aspect of local communities of this kind of housing area have a lot of problems while it also has a lot of good characteristics. A representative one is that age of the tenants is rising very swiftly and it makes the local community imbalanced. Nowadays many countries including Japan have tackled problems concerning housing estates constructed during the mass housing era and try to search for ways to reactivate so-called new town areas by utilisation of existing environmental resources such as building stock and ample green open space. In Japan many elemental technologies have been developed in order to utilise existing building stock. However, how to combine these technologies and new holistic methods for reactivation are still underdeveloped. Therefore, it is very important to fred these ways and to make a comprehensive plan for rehabilitation of these areas. The first purpose of our study is to develop and clarify how to organise and integrate many kinds of elemental techniques and the holistic measures for the improvement of both social and physical environment in suburban mass housing estates. Subsequently we try to reorganise proper relations between human settlements and the various service provision for those regions. Our last focus is put on searching for new ways to raise the value of existing housing environment. Our conclusion intends to indicate important of the master plan and its execution, where mass housing estates progress for the physical and social improvement.

A Modified Paving Approach and Automatic Mesh Grading Method to Quadrilateral Mesh Generation

A modified paving technique for automatic generation of all-quadrilateral mesh fromarbitrary 2-D geometry is presented. The generated mesh elementS are nearly square andperpendicular to boundaries. Aner the nodes and elementS formation is completed. a fully automaticgrading method is applied to increase the accuracy and reliability of engineering analysis. In thispaper, we mainly describe the theory of mathematical algorithm and present some examples ofautomatically generated mesh.

Finite Element Simulations of Crack Propagation in Al_(2)O_(3)/6061Al Composites

In this work, the local fracture initiation behaviour of an Al2O3/6061Al composite is studied numerically. The damage behaviour of the microstructure is evaluated in consideration of the path and the amount of damage as well as the stress-strain performance of the microstructure. The damage behaviour of the ductile matrix has been simulated using the damage parameter D. For the simulation of fracture of the ceramic particles, a normal stress criterion is applied. For the analysis of the damage behaviour of the transition zone between particulate and matrix, both damage models （D parameter and normal stress criteria） are applied in this region. Parameter studies of crack propagation prediction in the Al2O3/6061Al composite on the basis of an Element Elimination technique have been performed for two differently heat-treated variants resulting in different mechanical properties. In addition, residual stress effects on the damage behaviour are examined for various microstructural situations.

Heat transfer enhancement from heat sources using optimal design of combined fins heat-sinks

The rapid movement of heat transferred goes to be the most important target for researchers to deals with the thermal problems of electronic systems.Especially,that has high packing densities in limited space.Consequently,vertical combination between two shapes of fins was considered to improve the thermal performance of heat sink.Here,many models(longitudinal-pin fins)were created as a new approach based on the stable both of material and size.In the analytical solution,Finite element techniques used to solve the mathematical modeling and signum-sinusoidal-signum function was modified to model both the variable heat transfer area and convection perimeter.While in the numerical procedure,ANSYS simulation used as the validation of temperature distribution.In addition,results from previous work were used as second method of validation process.The results show a high level of agreement by maximum difference does not exceed(3.52%).In the calculation process,natural convection,range of Ra number(105–107)were applied for all models of which each one is distinguished by the parameter of area ratio(A∗)between hybrid model and longitudinal model.The results show many advantages;a significant drop in temperature profile about(2.7%–8.8%).Also,decrease in thermal resistance by(23%–43%)and increases in heat transferred(29%–78%).Furthermore,all parameters have a significant improve for the models that have A∗<1.48.But this improvement was down to less level at A∗>1.48 as a result of overlapping between the effects of miscellaneous parameters.Irreversibility that associated with the entropy generation was considered.In this step,it becomes important to find the model that achieves maximize of the thermal performance and minimize of the entropy generation.For that,the optimization procedure using genetic algorithm was adopted.It's clearly the best model exist within a close range between 1.509 and 1.518 based on the behavior of the best fitness function.