The unified mechanics theory (UMT) is ab-initio unification of the second law of thermodynamics and Newton's universal laws of motion, in which Boltzmann's second law of entropy formulation governs dissipation & degradation. Hence, the unified mechanics theory does not require any empirical dissipation & degradation potential function or an empirical void evolution function. Material degradation is quantified on the Thermodynamic state index (TSI) axis based on the specific entropy production, which starts at zero and asymptotically approaches one at failure.
The unified mechanics theory (UMT) was used to develop a model to predict the fatigue life of pre-corroded steel samples with BCC structure. Details of the experimental validation are also provided.
Thin films usually exhibit instabilities and yield intricate wrinkles when two clamped ends are twisted. Here, we explore the wrinkling behavior and pitch-fork bifurcation of twisted thin films experimentally and theoretically. To quantitatively predict the post-buckling evolution of twist-induced wrinkling morphology, we develop a refined finite-strain plate model derived from 3D field equations and then solve it by using the finite element method with COMSOL. We examine the effects of aspect ratios and pre-tension on the wrinkling profile.
A bistable curved beam with magnetic torque-driven actuation has the potential for fast and untethered reconfiguration of metamaterials. However, no modeling method of a bistable curved beam whose instability is coupled with an external magnetic field for the design of active metamaterials. A bistable curved beam's second mode (S-shape) generation is essential for a multimodal and multistep reconfiguration of metamaterials, which was not explored before.
We present the first mixed mode phase-field model of ductile fracture. The contribution of crack opening and shearing deformations to the propagation of a crack is expressed by introducing two phase fields. Constitutive relations are then introduced to couple and distinguish these phase fields. Special attention is given to the maximum shear stress and its effect on the development of fractures. The proposed model is validated by tensile testing experiments found in the literature on Al 2024 T-351.
Extreme Mechanics Letters (EML) is pleased to announce the initiation of an EML - Early Career Advisory Board (EML-ECAB) program to promote outstanding early career researchers and engage them in a path towards editorial services and contributions.
This work presents a geometrically exact Kirchhoff-like electroelastic rod theory wherein the contribution of free space energy is also factored in. In addition to the usual mechanical variables such as the rod's centerline and cross-section orientation, three electric potential parameters are also introduced to account for the variation in electric potential within the rod's cross-section as well as along the rod length. The free space energy is included through an electric flux-like variable acting on the lateral surface of the rod.
In this paper we formulate the initial-boundary value problem of accreting circular cylindrical bars under finite torsion. It is assumed that the bar grows as a result of printing stress-free cylindrical layers on its boundary while it is under a time-dependent torque (or a time-dependent twist) and is free to deform axially. In a deforming body, accretion induces eigenetrains, and consequently residual stresses. We formulate the anelasticity problem by first constructing the natural Riemannian metric of the growing bar.
Multiscale mechanics and extreme materials lab (https://z.umn.edu/ravi-research-lab) at the University of Minnesota Twin Cities has two fully funded Ph.D. positions starting in fall 2023. Interested candidates may reach out to sravi@umn.edu.
For orthotropic plane strain problems, the various existing calculation methods are very complex. The orthotropic plane strain problem with cracks have solved by using a new element model, and compared with the finite element method, it can be found that the displacements and the stresses of the two methods are in good agreement. Supplemental Videos: (1) https://www.bilibili.com/video/BV1QW4y1e7YQ/?spm_id_from=333.999.0.0
This work presents a modified phase-field model for accurate coupling of phase transformation and cracking in shape memory ceramics. The existing phase-field models underestimate the elastic response at the beginning of the mechanical response. We modified the chemical free energy to control the rate of phase transformation and consequently obtain a physical elastic response before initiation of phase transformation. First, the forward and reverse martensitic phase transformation in a superelastic single crystal 3 mol% yttria-stabilized tetragonal zirconia is studied.
ASME Aerospace Division is launching a new conference called ASME Aerospace Structures, Structural Dynamics, and Materials (SSDM) Conference. The mission of this conference is to convene and serve the global aerospace structures, structural dynamics, and materials communities, continuing the legacy left behind by the AIAA/ASME/ASCE/AHS/ASC SDM conference. SSDM accepts two types of submissions: Paper (abstract deadline: Nov. 14) and Presentation Only (deadline: Feb. 13). The inaugural conference will be held in San Diego (June 19-21 2023).
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