The three-point bending test is a valuable method for evaluating the mechanical properties of 3D-printed biomaterials, which can be used in various applications. The use of 3D printing in specimen preparation enables precise control over material composition and microstructure, facilitating the investigation of different printing parameters and advanced materials. The traditional approach to analyzing the mechanical properties of a material using a three-point bending test has the disadvantage that it provides only global information about the material’s behavior. This means that it does not provide detailed insight into the local strain distribution within the material. However, the 2D Digital Image Correlation (DIC) method offers additional insight, especially in terms of strain localization. DIC is an optical technique that measures full-field displacements and strains on the surface of a sample. PLA and enhanced PLA-X material were utilized to create three-point bending samples. The aim of this paper was to analyze and compare the influence of aging on the mechanical properties of PLA and enhanced PLA-X materials using three-point bending coupled with the DIC method. The results showed statistically significant differences between the PLA and PLA-X, for both the new and aged materials. The aged PLA samples had the highest average value of maximal force around 68 N, which was an increase of 8.8% compared to the new PLA samples. On the other hand, the aged PLA-X material had an increase of 7.7% in the average maximal force compared to the new PLA-X samples. When comparing the two materials, the PLA samples had higher maximal force values, 6.2% for the new samples, and 7.3% for the aged samples. The DIC results showed that both the new PLA and PLA-X samples endured higher strain values at Points 1 and 2 than the aged ones, except for the aged PLA-X sample at Point 2, where the new sample had higher strain values. However, for the first 5 min of the experiment, both materials exhibited identical behavior, after which point significant differences started to occur for both materials, as well as at Points 1 and 2. A more profound comprehension of the biomechanical characteristics of both PLA and PLA-X material is essential to enhance the knowledge for potential biomedical applications. The DIC method was found to be a powerful tool for analyzing the deformation and failure behavior of samples and for complementing the traditional approach to material testing.

Data on the strain and stress status of the pipe in the circumferential direction are required for various pipe manufacturing procedures (e.g., in the oil business, the process of manufacturing seamless pipes with a conical shaft). The aim of this study is to develop a procedure to determine the strain and stress behavior of Pipe Ring Tensile Specimens (PRTSs) in the hoop direction, as there are a lack of official standardized methods for testing PRTS. This paper discusses the application of the Digital Image Correlation method for testing plastic PRTSs. PRTSs are tested using a specially designed steel tool with two D blocks. A 3D-printed PRTS is placed over two D-shaped mandrels, which are fixed on a tensile tool and tensile testing machine. The strain evolution in the gage length of the specimens is captured using the three-dimensional Digital Image Correlation (3D DIC) method. To check the geometry of the cross-section of the PRTS after fracture, all the specimens are 3D scanned. For the study, six groups of PRTS are analyzed, consisting of three filling percentages (60, 90, and 100%) and two geometry types (Single and Double PRTS). The results show that the type and percentage of filling, as well as the method of printing, affect the material behavior. However, the approach with the DIC system, 3D printer, and scanner shows that they are effective instruments for mapping complete strain fields in PRTS, and thus are effective in characterizing the mechanical properties of pipes.

This paper presents a part of development of a non-standard method for testing of cylindrical test specimens for measurement of fracture properties of pipeline materials. This method for testing of cylindrical structures working under pressure is based on determining of fracture mechanics parameters on SENT (Single Edge Notched Tension) specimens and new PRNT (Pipe Ring Notched Tension) specimens. In this work, both types of specimens required for this testing were manufactured from polyamide PA12 by using SLS (selective laser sintering) additive manufacturing method. Testing of the specimens is performed on the universal device for testing of mechanical properties of materials Shimadzu, AGS-X 100 kN. The tensile testing is accompanied by GOM Aramis 2M system, used for digital image correlation. By using these two systems, test results are obtained for ring-shaped and SENT specimens, including forces, displacements and fracture mechanics parameters CMOD (Crack Mouth Opening Displacement) and CTOD-?5 (Crack Tip Opening Displacement obtained by ?5 technique), as well as crack growth. Repeatability of this process, along with valid result consistency, represent the basis for further development of the new method, including the determining of energy-based fracture mechanics parameters: J integral and stress intensity factor.

This paper presents new methodology for determining the actual stress–strain diagram based on analytical equations, in combination with numerical and experimental data. The first step was to use the 3D digital image correlation (DIC) to estimate true stress–strain diagram by replacing common analytical expression for contraction with measured values. Next step was to estimate the stress concentration by using a new methodology, based on recently introduced analytical expressions and numerical verification by the finite element method (FEM), to obtain actual stress–strain diagrams, as named in this paper. The essence of new methodology is to introduce stress concentration factor into the procedure of actual stress evaluation. New methodology is then applied to determine actual stress–strain diagrams for two undermatched welded joints with different rectangular cross-section and groove shapes, made of martensitic steels X10 CrMoVNb 9-1 and Armox 500T. Results indicated that new methodology is a general one, since it is not dependent on welded joint material and geometry.

This article aims to investigate the mechanical characteristics of specimens fabricated using Selective Laser Sintering technology. The research covers flexural specimens, produced by PA12 materials. CAD model dimensions were selected according to the ISO 178 standard, and the chosen specimen geometry is 96 x 8 x 4 [mm] in bulk. All specimens were produced using a specialized machine Fuse 1 (FormLabs, Summerville, MA). Four specimen batches were produced, each with a different printing orientation (i.e. vertical and horizontal) and location on the printing plate (i.e. in the middle and on the edge of the powder bed). The specimens are tested using a Shimadzu universal machine for testing the mechanical characteristics of materials, AGS-X 100 kN, with a unique additional tool for testing 3-point bending specimens.

Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3-D digital image correlation method. Numerical analysis was done in ANSYS software package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application.