A study of contact methods in the application of large deformation dynamics in self-contact beam

This paper introduces a procedure in the field of computational contact mechanics to analyze contact dynamics of beams undergoing large overall motion with large deformations and in self-contact situations. The presented contact procedure consists of a contact search algorithm which is employed with two approaches to impose contact constraint. The contact search task aims to detect the contact events and to identify the contact point candidates that is accomplished using an algorithm based on intersection of the oriented bounding boxes (OBBs). To impose the contact constraint, an approach based on the complementarity problem (CP) is introduced in the context of beam-to-beam contact. The other approach to enforce the contact constraint in this work is the penalty method, which is often used in the finite element and multibody literature. The latter contact force model is compared against the frictionless variant of the complementarity problem approach, linear complementarity problem approach (LCP). In the considered approaches, the absolute nodal coordinate formulation (ANCF) is used as an underlying finite element method for modeling beam-like structures in multibody applications, in particular. The employed penalty method makes use of an internal iteration scheme based on the Newton solver to fulfill the criteria for minimal penetration. Numerical examples in the case of flexible beams demonstrate the applicability of the introduced approach in a situation where a variety of contact types occur. It was found that the employed contact detection method is sufficiently accurate when paired with the studied contact constraint imposition models in simulation of the contact dynamics problems. It is further shown that the optimization-based complementarity problem approach is computationally more economical than the classical penalty method in the case of studied 2D-problems.

An Efficient Contact Search Algorithm for Three-Dimensional Sphere Discontinuous Deformation Analysis

The efficiency of contact search is one of the key factors related to the computational efficiency of three-dimensional sphere discontinuous deformation analysis (3D SDDA). This paper proposes an efficient contact search algorithm, called box search algorithm (BSA), for 3D SDDA. The implementation steps and data structure for BSA are designed, with a case study being conducted to verify its efficiency. The data structure also has been improved for parallelizing the computation in contact search. For the demonstration of the proposed algorithm (BSA), six cases with various sphere numbers are simulated. Simulation results show that the time consumed in contact search using BSA (CTofBSA) is much less than that by the direct search algorithm (DSA) (CTofDSA). For the case with 12,000 spheres, CTofBSA is 1.1[Formula: see text]h, which is only 1.3% of CTofDSA (84.62[Formula: see text]h). In addition, the proportion of the computation quantity of contact search in the entire computation (Pcs) is 91.3% by using DSA, while this value by BSA is only 12.4%, which demonstrates the contribution of BSA. The efficiency brought about by BSA (time consumed and computation quantity) may enable 3D SDDA to simulate large-scale problems.

COPING STRATEGIES AS DETERMINANTS OF READINESS FOR AGE-RELATED CHANGES

he article analyzes the topical matter of psychological mechanisms of awareness by person of own age. The problem is considered through study of relationship between the coping and subjective willingness to adopt age-related changes throughout the life. The aim of the article was to study features of the coping strategies as determinants of psychological readiness for age-related changes adoption in people of various ages (19-85 years old). Four hundred three inhabitants of four regions of Ukraine were surveyed, involving: 95 persons ‒ inhabitants of the Southern Ukraine (23.6%), 100 persons ‒ residents of the Eastern Ukraine (24.8%), 108 persons – residents of the Central Ukraine (26.8%), 100 persons – residents of the Western Ukraine (24.8%). The method of readiness for age-related changes (N.S. Gluhanyuk, T.B. Gershkovich) and the SACS coping questionnaire (S. Hobfoll with co-authors) were used. It was found that components and levels of readiness for age-related changes adoption are determined by a number of coping strategies that are characterized by the prosocial coping vector, which is guided by future-oriented processes. It was shown that the coping has the most important value in formation of readiness for age-related changes adoption at the age under 35 years old. During this age period, the strategies activation of making social contact, search for social support, as well as the avoidance strategies suppression, play the most important role in integral readiness provision. The basic assumption of the research was confirmed related to the coping strategies as determinants of psychological readiness for age-related changes adoption. The fact determined in our research related to the avoidance coping strategies, as negative predictor of readiness for age-related changes adoption, corresponds to the data that acceptance of thoughts of aging intensifies and stabilizes the experience of transformational aging. The idea, debated in literature, of proactive and anticipatory-preventive attitude towards age-related changes adoption, which enables the efficient coping of age-related changes, was also confirmed in the research performed.

Validation of the modified digital element approach for simulating ballistic impact against fragment simulating projectile

A modified digital element approach (DEA) is applied to simulate fabric perforation process under ballistic impact. The previous version of the DEA is capable of simulating ballistic impact of textile fabric using rigid body spherical and cylindrical projectiles only. Fragment simulating projectile (FSP) and real bullets are not modeled. The subject of this research is to perform ballistic penetration process against projectile of arbitrary shape and validate the modified DEA. A fabric to solid body projectile contact search and contact force calculation algorithm is established. Ballistic impact of textile fabrics against spherical and cylindrical projectiles is performed using the previous DEA and the modified DEA separately. Numerical results are compared to the well published DEA results to investigate the fabric bullet resistant performance.