Marko Čanađija

Stress-driven modeling of nonlocal thermoelastic behavior of nanobeams

Abstract A consistent stress-driven nonlocal integral model for nonisothermal structural analysis of elastic nano- and microbeams is proposed. Most nonlocal models of literature are strain-driven and it was shown that such approaches can lead toward a number of difficulties. Following recent contributions within the isothermal setting, the developed model abandons the classical strain-driven methodology in favour of the modern stress-driven elasticity theory by G. Romano and R. Barretta. This effectively circumvents issues associated with strain-driven formulations. The new thermoelastic nonlocal integral model is proven to be equivalent to an adequate set of differential equations, accompanied by higher-order constitutive boundary conditions, when the special Helmholtz averaging kernel is adopted in the convolution. The example section provides several applications, thus enabling insight into performance of the formulation. Exact nonlocal solutions are established, detecting also new benchmarks for thermoelastic numerical analyses.

Thermomechanics of Beam-Like Nanostructures

Abstract This chapter starts with a short introduction to the nonlocal continuum mechanics that will serve as a cornerstone for elaborations that follow. Presented nonlocal theory will be applied to the problems involving beams of very small dimensions, i.e., nanobeams. Since observations at micro- and nanoscale determined sensitivity of such beams to the small size effects, the nonlocal theory seems to be a perfect choice for prediction of mechanical behavior of such structures. Consequently, the presented theory can be also applied to the corresponding problems at microscale. Bernoulli-Euler and Timoshenko beam formulations are considered, with special emphasis on the influence of nonisothermal environments on the deformation and stresses under static load of both mechanical and thermal nature. Initially, the presented theory considers beams made of homogeneous isotropic materials and is subsequently extended to more complex case of functionally graded materials. The performance of presented theoretical models is illustrated on several examples.

A Multiscale Framework for Thermoplasticity

The chapter describes a homogenization procedure for thermoplasticity problems. The proposed model is suitable for the finite strain regime and supports a very wide class of plasticity models. The methodology starts from the thermodynamically consistent thermoelastic framework already described in the literature. The latter framework is now extended to account for inelastic deformations. The problem is separated by means of the isothermal split into a mechanical and a thermal step, both at the macroscale and the microscale. As demonstrated in an example, the method does provide a way to successfully homogenize microscale variables as well as tangent operators. Finally, limitations of the approach are pointed out.

On the influence of thermal stresses on eigenvalues of a circular saw blade

The paper presents a thermomechanical analysis of a circular saw with the emphasis on the influence of thermal stresses on eigenmodes. Significance of the slot’s length was also investigated. The transient thermal analysis was carried out, and based on the obtained temperature field, the modal analysis was performed accounting for both thermal and centrifugal stresses. It was found that thermal stresses have a profound influence on eigenvalues. The results clearly indicate a necessity of performing analyses of this kind in order to obtain an efficient design of the circular saw. At the end, main findings are emphasized once more.

Uniaxial Properties versus Temperature, Creep and Impact Energy of an Austenitic Steel

Abstract In this paper, uniaxial material properties, creep resistance and impact energy of the austenitic heat-resistant steel (1.4841) are experimentally determined and analysed. Engineering stress–strain diagrams and uniaxial short-time creep curves are examined with computer-controlled testing machine. Impact energy has been determined and fracture toughness assessed. Investigated data are shown in the form of curves related to ultimate tensile strength, yield strength, modulus of elasticity and creep resistance. All of these experimentally obtained results are analysed and may be used in the design process of the structure where considered material is intended to be applied. Based on these results, considered material may be classified as material of high tensile strength (688 MPa/293 K; 326 MPa/923 K) and high yield strength (498 MPa/293 K; 283 MPa/923 K) as well as satisfactory creep resistance (temperature/stress →

Associative coupled thermoplasticity at finite strain with temperature-dependent material parameters

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Application of gradient elasticity to armchair carbon nanotubes: Size effects and constitutive parameters assessment

strain (%) at 1,200 min: 823 K/167 MPa →

On functionally graded Timoshenko nonisothermal nanobeams

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A gradient elasticity model of Bernoulli–Euler nanobeams in non-isothermal environments

0.25 %; 923 K/85 MPa →

Low cycle fatigue and mechanical properties of magnesium alloy Mg–6Zn–1Y–0.6Ce–0.6Zr at different temperatures

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