Experimental Research of Selected Lattice Structures Developed with 3D Printing Technology

This paper presents the results of the experimental research of 3D structures developed with an SLA additive technique using Durable Resin V2. The aim of this paper is to evaluate and compare the compression curves, deformation process and energy-absorption parameters of the topologies with different characteristics. The structures were subjected to a quasi-static axial compression test. Five different topologies of lattice structures were studied and compared. In the initial stage of the research, the geometric accuracy of the printed structures was analysed through measurement of the diameter of the beam elements at several selected locations. Compression curves and the stress history at the minimum cross-section of each topology were determined. Energy absorption parameters, including absorbed energy (AE) and specific absorbed energy (SAE), were calculated from the compression curves. Based on the analysis of the photographic material, the failure mode was analysed, and the efficiency of the topologies was compared.

The influence of friction on gas parameters in the minimum section of nozzles

Processes of gas flow in nozzles, accompanied by the release of frictional heat, are presented in the form of polytropic processes. The polytropic process index n determines the degree of irreversibility of the gas flow process caused by the release of frictional heating. Relations are obtained to calculate the flow rate and thermodynamic properties of gas in the minimum section of the Laval nozzle and in the outlet section of the convergent nozzle at a pressure behind the nozzle less than the critical pressure. The gas calculated parameters (pressure, temperature, specific volume, velocity, cross-sectional area) in the minimum cross-section differ from the recommended values in the reference literature [1]. In particular, the gas pressure in the minimum cross section turns out to be higher than the critical pressure recommended in [1].

Application of the Ford-Falkerson algorithm to detect excess information

The object of the article is the network maximum flow algorithm, mainly the Ford-Fulkerson algorithm. The algorithm began to be developed by two scientists: Ford and Fulkerson. This algorithm was proposed in order to find the maximum flow in the network. They began to be actively studied by scientists from the middle of the last century. The first report of "Maximum Network Flow" dates back to 1954. The authors of the report, Ford and Fulkerson had proved the theorem on the maximum flow and the minimum cross section for non-oriented graphs: the value of the maximum flow in the network is equal to the minimum throughput capacity of the section. The interest in the solution of these tasks was primarily due to practical needs, for that time construction of routes for the transportation of raw materials was not optimal and transported more raw materials than can transfer the connection between points. Such problems often arise when constructing connections that transport oil through pipes or transport coal through special excavators. The subject of the article is the problem of finding the maximum flow in the network. In graph theory, the transport network is an indicative graph in which each arc has no negative throughput and flow. Two peaks are distinguished: source and drain - such that any other vertex in the network lies on the way from source to drain. The article consists of two sections. In the first section we consider the mathematical formulation of the problem and concrete examples of problems. The second section examines the classic Ford-Fulkerson algorithm, the modified Ford-Fulkerson algorithm to find excess information on the network, and the work of a modified algorithm on a specific example from the first section. The considered problems are relevant both from a theoretical and a practical point of view.

Influence of standard recommendations for the calculation of the column-base connection by socket according to ABNT NBR 9062:2006

This work studies the column-base connection by external socket in precast structures. A parametric study of the geometric characteristics of the external socket base with smooth interface is presented. In this parametric study, the consumption of concrete and steel are analyzed. The column cross section, the embedded length of the column in the socket base and the thickness of the wall of the socket base were the variables considered in this study. It was observed that with the increase of the embedded length, the minimum cross section of the main horizontal reinforcement reduces. With this modification, the walls of the socket base that are perpendicular to the direction of the applied loads presented a reduction of their stiffness. Besides the parametric study, this paper presents a verification model. This part of the study shows the possibility to generate abacuses that simplifies the project of the socket base foundation. Moreover, a comparative analysis becomes easier to be accomplished

Investigation of the Shape of a Cruciform Biaxial Tensile Specimen Intended for a Combination of Plane Strain Tensile States

This study investigates the shape of a cruciform specimen that is stretched in the normal direction of the minimum cross section using FEM. In addition, plane strain tensile states exist in the measurement region in order to determine the forming limit diagram not by an arbitrary stress ratio but by the strain ratio. We propose two types of cruciform specimens. One is a flat-type cruciform specimen, which has deep slits in the middle of the arm region in the width direction. The other specimen is a reduced measurement region type, which also has deep slits as well as a shape that is a biaxial combination of two plane strain tensile specimens. We analyze equibiaxial tensile tests of these two proposed cruciform specimen types using FEM.

Influence of Processing Route on the Work-Hardening and Ductile Fracture of an AA6060 Aluminium Alloy

Tensile tests on smooth and notched axisymmetric specimens were carried out to determine the large strain work-hardening curves and the ductile fracture characteristics of an AA6060 aluminium alloy for three different processing routes. The alloy was processed in three subsequent steps: 1) casting and homogenization, 2) extrusion, and 3) cold rolling and heat treatment to obtain a recrystallized grain structure. After each processing step, the material was tested after natural ageing for more than one week. A laser-based extensometer was used to continuously measure the average true strains to failure in the minimum cross-section of the specimens and the true stress-strain curves were calculated. Since these curves are influenced by necking, they do not represent the correct work-hardening of the material. Accordingly, finite element (FE) simulations of the tensile tests on the smooth axisymmetric specimens were conducted to determine the work-hardening curves to failure, using an optimization tool that interfaced with the nonlinear FE code and the experimental stress-strain curves as objectives. The microstructure of the alloy was characterized after the three processing steps by optical and scanning electron microscopy, and fractography was used to investigate the failure mechanisms.

Optimization Design of the Gas Station Roof Based on Analysis

A mathematic model on the optimum design of the gas station roof was established, and made an optimization to its grid structure parameters by the finite element software ANSYS.According to the actual condition of work and on the premise of meeting the need, the minimum cross section of the grid structure was determined. The results indicate that materials and cost can evidently decreased by optimum analysis method.

Study on the Residual Strength Assessment Method on Corroded Subsea Pipeline Based on Reference Stress Method

In this paper, the reference stress method is adopted in the residual strength assessment of corroded subsea pipeline. Through the monitoring of the von Mises stress σlocal in the minimum cross section, the relationship between the stress response and input pressure is found. Then, based on this relationship, a simple and effective method to assess the residual strength of corroded subsea pipeline is proposed. Through the comparison with experimental results, the accuracy and reliability of this method is confirmed.

Flow in a Corrugated Channel With Multiple Heat Sources

Numerical method based on the finite element method is utilized to study the heat transfer enhancement from discrete heat sources using a wavy channel. The considered geometry consists of a channel formed by two wavy plates with six discrete heat sources placed on upper and lower walls. The effect of the Reynolds number, Prandtl number, waviness of the wavy wall, and the location of the heat sources on the heat transfer out of the heat sources is investigated. The result indicates that the wavy channel significantly enhances the heat flow out of the heat sources, and heat sources located at the minimum cross section areas of the channel shows the best performance. The heat transfer enhancement can reaches as high as 120% for high Reynolds numbers and waviness of the channel.