Negative Poisson’s Ratio (or NPR) is the primary mechanical property of auxetic metamaterials that results in an improved mechanical performance compared to regular material arrangements [1]. The distinctive characteristics that are usually improved are stiffness and impact resistance due to selective and controlled densification [2]. The paper explores the effects of changing the parameters of a cylindrical auxetic structure under static and dynamic conditions on the mechanical characteristics. The auxetic cylinder shell was constructed using 2D auxetic unit cells.

Finite Element Analysis (FEA) through the ABAQUS simulation software was used to model quasi-static compression and impact loading for the auxetic structures. This analysis included a mesh-convergence study to ensure the suitability of mesh resolution for the accuracy of the model results. The change in the aspect ratio (ratio of the height to the diameter) of the cylinder structure and the radial thickness of 2D auxetic unit cells were performed, while the size of the unit cells was kept constant. The change in these parameters was found to change the mechanical properties of the overall structure. The cubical configuration with the aspect ratio close to unity provides NPR values close to 1 as well, while the change in the stiffness depends on the scale of the structure. Such processes can be used to tailor the Poisson’s Ratio and stiffness of lightweight cylinder auxetic structures for different applications.

To enhance the lifetime of mechanical system such as automobile, new reliability methodology – parametric Accelerated Life Testing (ALT) – suggests to produce the reliability quantitative (RQ) specifications—mission cycle—for identifying the design defects and modifying them [1]. It incorporates: (1) a parametric ALT plan formed on system BX lifetime that will be X percent of the cumulated failure, (2) a load examination for ALT, (3) a customized parametric ALTs with the design alternatives, and (4) an assessment if the system design(s) fulfil the objective BX lifetime. So we suggest a BX life concept, life-stress (LS) model with a new effort idea, accelerated factor, and sample size equation. This new parametric ALT should help an engineer to discover the missing design parameters of the mechanical system influencing reliability in the design process. As the improper designs are experimentally identified, the mechanical system can recognize the reliability as computed by the growth in lifetime, LB, and the decrease in failure rate. Consequently, companies can escape recalls due to the product failures from the marketplace. As an experiment instance, two cases were investigated: 1) problematic reciprocating compressors in the French-door refrigerators returned from the marketplace and 2) the redesign of hinge kit system (HKS) in a domestic refrigerator. After a customized parametric ALT, the mechanical systems such as compressor and HKS with design alternatives were anticipated to fulfil the lifetime – B1 life 10 year.

Establishing process-structure-property (PSP) relationships is essential for optimizing manufacturing techniques, yet it often requires extensive, costly experimentation. This is particularly true for additive manufacturing (AM), where numerous process parameters complicate the task. Our research introduces an interpretable machine learning strategy to predict and refine the process window for laser powder bed fusion (LPBF), while also delineating PSP relationships. We utilized Gaussian process regression (GPR) to model various inputs, such as process parameters and microstructural features, to predict key mechanical properties. The adaptability of the GPR model, through hyperparameter tuning for each input, facilitates feature selection and enhances model transparency. This methodology not only identifies pivotal factors influencing mechanical performance but also clarifies PSP relationships in additive manufacturing alloys, offering insights for customizing final material properties. Our approach is versatile, applicable across different additive manufacturing techniques and materials, and opens the door to achieving new mechanical properties and deeper PSP understanding.

It has only recently been discovered that the plastic deformation of solids is not "smooth" in either space or time. Elementary plastic deformation events—such as dislocation avalanches, mechanical twinning, and martensitic transformations—are typically hidden within deformation curves, which provide only averaged information. This concealment arises from the simultaneous plastic activity occurring at multiple locations within a sample, combined with the limited force and time resolution of conventional deformation devices.

In contrast, modern supplementary techniques—such as acoustic emission monitoring and high-resolution and/or ultra-fast imaging—enable detailed characterization of deformation mechanisms. We employ these techniques to study metallic materials across scales, from macro to micro, where deformation behavior becomes increasingly erratic. Using these methods, we can recognize spatial and temporal patterns in seemingly random plastic events by applying various statistical analyses.

As a practical example, we present deformation experiments, conducted using unique experimental setups, on metallic specimens ranging from the micron scale (micropillar) materials up to the complex bulk-scale high-entropy alloys exhibiting intriguing deformation dynamics. The findings advance the fundamental understanding of deformation dynamics in crystalline materials and provide valuable insights for the design of emerging micron-scale mechanical devices as well as next-generation metallic materials.

Metastable beta titanium alloys are perspective candidates for the use in the aircraft industry and medicine due to their excellent strength, relatively low modulus of elasticity and enhanced biocompatibility [1-2]. Thermomechanical treatments are often used to improve mechanical properties of these alloys due to the precipitation of different phases, namely the α- and ω-phase [3]. It is also well-known that the α-phase precipitation is heterogeneous and preferentially occurs at lattice defects. Thus, a high density of grain boundaries and dislocations is needed for a homogeneous nucleation of the α-phase.

A Ti15Mo, which is a representative of a simple binary metastable beta Ti alloy, in a beta solution treated condition was subjected to severe plastic deformation by high pressure torsion (HPT) aiming to introduce a high density of lattice defects to the material [4]. The material was subsequently subjected to several types of thermal treatments to examine the phase transformations occurring in the deformed material upon heating. 

In order to optimize the parameters of the thermomechanical treatment of the alloy and to achieve a material with required mechanical properties, the effects of the grain boundaries, dislocations, induced strain, ω-phase and local chemical inhomogeneities on phase transformations were examined in-situ by electrical resistivity and synchrotron X-ray diffraction and complemented by post mortem detail investigation of the microstructure and lattice defects in characteristic conditions by scanning and transmission electron microscopy including advanced techniques of transmission Kikuchi diffraction and automated crystallographic orientation mapping, positron annihilation spectroscopy, and X-ray diffraction [5-6]. 

Lattice defects introduced by SPD significantly influence both the phase transformations and the morphology of the α-phase. Lattice defects, in particular dislocations and grain boundaries, act as preferential nucleation sites for α precipitation and form fast diffusion paths for solutes which results in enhancement of phase transformations in the severely deformed material. On the other hand, mechanical properties of heat treated samples are mainly influenced by the hard and brittle ω-phase and this influence is superior to that of the strain imposed SPD.

It is well sound that the rigorous formulation of equations governing complex materials, where multi-scale and multi-physics phenomenon are present, still remains a big challenge in continuum mechanics e.g. [1]. Distribution of line and surface defects as dislocations and disclinations in the material implies such difficulties. Indeed, the classical divergence of a stress tensor as originally developed by Cauchy requires some subtil conditions which might sometimes underestimated. Such is the case when distribution of defects (i.e. elastoplasticity) occurs within an otherwise virgin material.

The goal of this work is to derive the generic shape of conservation laws, specially equilibrium equations of such complex material in mechanics. 

First, any mathematical equations governing physics models should be invariant under passive diffeomorphisms (i.e. change of coordinate system). We then propose a mathematical model of generalized continuum described by Lagrangian depending on metric, torsion and curvature of a Riemann-Cartan manifold [2]. 

Second, generic conservation laws of Noll first-gradient continuum (deduced rigorously by Lie derivative of metric) are extended to such generalized continuum by using active diffeomorphisms deduced by Lie derivatives of metric, torsion and curvature. The method thus uses the so-called Principle of General Covariance, based on these derivatives along a non-uniform vector field e.g.  [3].

The present work although devoted to conservation laws lies heavily on the geometric approach of generalized continuum. The main concern is then the derivation of equilibrium equations in various situations, and with some applications to defected materials or even other physics as gravitation. If time is allowed some application in coupled physics as electromagnetism will be sketched. Some hints for the use of non-smooth elastioplasticity may be presented.