Conventionally, plastic anisotropy is calibrated by using standard uniaxial tensile and biaxial test results. Alternatively, heterogeneous strain field specimens in combination with full-field measurements can be used for this purpose. As reported by the literature, such an approach reduces the number of required tests enormously, but it is challenging to obtain reliable results. This paper presents an alternative methodology, which represents a compromise between the conventional and heterogeneous strain field calibration technique. The idea of the method is to use simple tests, which can be conducted on the uniaxial testing machine, and to avoid the use of advanced measuring equipment. The procedure is accomplished by conducting standard tensile tests, which are simple and reliable, and by a novel heterogeneous strain field tensile test, to calibrate the biaxial stress state. Moreover, only two of the parameters required for full characterisation need to be inversely identified from the test response; the other parameters are directly determined from the uniaxial tensile test results. This way, a dimension of optimization space is reduced substantially, which increases the robustness and effectiveness of the optimization algorithm.

Quadruple glazing has become a high-end standard in the field of sealed insulating glass units. With more than three glass panes a set of internal heat-related technical problems emerges. Durability, being the most pressing problem, requires careful management of the primary sealant deformation, especially under summer environmental conditions. Namely, the role of the primary seal in insulating glass units is to protect their humidity-sensitive, low-emissivity coatings from moisture and the quality of such protection is a key factor in durability. In this paper, a new methodology is proposed for a feasibility assessment of a new multipane insulating glass unit design, where proper design enables avoidance of excessive strain on the primary seal. It focuses on the calculation of the primary sealant strains, which are nonhomogeneous and multiaxial according to different loading conditions. This approach leads to analytical expressions that enable convenient identification of the critical location on the primary sealant. Finally, feasibility is assessed with the proposed methodology for the newly developed highly insulative six-pane facade unit by means of a comparison of the calculated strain state with the anticipated allowable strains, based on technical practice.

Purpose: The purpose of this study, which is designed for the implementation of models in the implicit finite element framework, is to propose a robust, stable and efficient explicit integration algorithm for rate-independent elasto-plastic constitutive models. Design/methodology/approach: The proposed automatic substepping algorithm is founded on an explicit integration scheme. The estimation of the maximal subincrement size is based on the stability analysis. Findings: In contrast to other explicit substepping schemes, the algorithm is self-correcting by definition and generates no cumulative drift. Although the integration proceeds with maximal possible subincrements, high level of accuracy is attained. Algorithmic tangent stiffness is calculated in explicit form and optionally no analytical second-order derivatives are needed. Research limitations/implications: The algorithm is convenient for elasto-plastic constitutive models, described with an algebraic constraint and a set of differential equations. This covers a large family of materials in the field of metal plasticity, damage mechanics, etc. However, it cannot be directly used for a general material model, because the presented algorithm is convenient for solving a set of equations of a particular type. Practical implications: The estimation of the maximal stable subincrement size is computationally cheap. All expressions in the algorithm are in explicit form, thus the implementation is simple and straightforward. The overall performance of the approach (i.e. accuracy, time consumption) is fully comparable with a default (built-in) ABAQUS/Standard algorithm. Originality/value: The estimated maximal subincrement size enables the algorithm to be stable by definition. Subincrements are much larger than those in conventional substepping algorithms. No error control, error correction or local iterations are required even in the case of large increments.