This paper presents the results of an investigation of the possibility of the reliable determination of the residual stress–strain state in polymers and composites using a combination of bridge curvature, optical scanning, and finite element methods. A three-factor experiment was conducted to determine the strength of printed PLA plastic products. The effect of the residual stresses on the strength of the printed products was evaluated. By comparing the values of the same strength stresses, a relationship between the nature of the stresses and the strength of the samples was found. A tendency of the negative influence of tensile stresses and the opposite strengthening effect of compressive stresses was obvious, so at the same values of tensile strength, the value of residual stress of 42.9 MPa is lower than that of the fibre compression at the value of 88.9 MPa. The proposed new methods of the residual stress determination allow obtaining a complete picture of the stressed state of the material in the investigated areas of the products. This may be necessary in confirming the calculated models of the residual stress–strain state, clarifying the strength criteria and assessing the quality of the selected technological modes of manufacturing the products.

This paper addresses the problem of synthesizing four-link initial kinematic chains with rotational pairs for designing flat lever mechanisms with specified motion laws of the input and output links. The proposed method formulates the synthesis problem as an optimization process involving three moving planes Q, Q1 and Q2. Each plane performs distinct motions: Q is fixed, Q1 rotates around a point A, and Q2 undergoes plane-parallel motion. The goal is to determine the optimal position of point A∈Q, B∈Q1 and C∈Q2 such that the distance between points B and C remains nearly constant across multiple configurations. The synthesis problem is reduced to a sequence of linear systems of equations corresponding to three iterative minimization stages: Determining the fixed-point A and the radius R for given points B and C; Determining the point B and radius R for a given point C; Determining the point C and radius R for a given point B. The algorithm uses a hierarchical optimization process to iteratively refine the positions of A, B, and C until convergence is achieved. The convergence criteria are defined by the small changes in the positions of these points and the radius R between iterations. The proposed method avoids solving a highly nonlinear system directly by decomposing the problem into simpler linear systems, ensuring computational efficiency and robustness. The solution provides the desired positions of the points, forming an open kinematic chain ABCD with three degrees of freedom. The approach is applicable to the synthesis of complex planar mechanisms with unrestricted parameters, making it a valuable tool for mechanism design.

This study presents the kinematic synthesis of planar mechanisms using precision point analysis for three, four, and five target positions. The research explores the application of graphical synthesis techniques to design mechanisms that accurately follow prescribed motion paths. Various configurations are examined, comparing their synthesized motion with theoretical precision points to evaluate the accuracy and feasibility of the proposed designs. Additionally, numerical optimization methods are considered to refine the results and improve motion fidelity. The study also extends the discussion to higher-order synthesis, incorporating additional precision points for improved accuracy in motion generation. The graphical results highlight the effectiveness of the synthesis approach, demonstrating its applicability to practical mechanism design. The findings contribute to the understanding of planar mechanism synthesis and provide insights into enhancing design methodologies for motion control applications. This paper presents GIM software, an educational and research software designed to facilitate the kinematic analysis of planar mechanisms. The software was developed to address the challenges students face in understanding kinematic theory and mechanism synthesis, providing an interactive and user-friendly platform for modeling and analyzing n-degree-of-freedom linkages.