Revista UIS Ingenierías

Generation of Numerical Models of Extension Springs Based on Images

2025-02-12T21:38:49+00:00

Non-standard springs manufactured in Ecuador show geometric deviations from design assumptions, affecting their performance and reliability. As an alternative to testing with specialized machines to assess their mechanical behavior, a procedure based on computer vision and numerical modeling of the spring is suggested. This work presents a step forward in this direction through a methodology to construct a numerical model of the real geometry of the spring using photographs and image processing algorithms. A photographic setup is created that makes it easier to take images in orthogonal directions, and the images are processed using the OpenCV library in Python to define points that describe the path of the spring wire. These points are converted into a finite element mesh to simulate the mechanical behavior of the spring. To validate the methodology, a geometric compliance check of the model with the spring is performed, and the actual and simulated force-displacement curves are compared. The results show good geometric compliance and an excellent match between the experimentally obtained and simulated stiffness constants.

Development of a field metallographic replica procedure for CA6NM stainless steel hydraulic runners

2024-08-01T14:45:27+00:00

Pelton and Francis hydraulic runners, alongside other components of hydroelectric turbine generators, are typically made in soft martensitic stainless steels, especially grade CA6NM from ASTM A743 standard, also known as 13-4. These hydromechanical components may experience deterioration during service due to the occurrence such as cracks or fractures, as well as wear associated with cavitation or erosion. Commonly, defects are repaired using conventional

welding processes employing electrodes with chemical composition, microstructure, and mechanical properties like those of CA6NM. However, these weld repairs not only lead to residual stresses but also to weld deposits and heat-affected zones (HAZ) with martensitic microstructures that make the components susceptible to hydrogen-induced cracking (HIC) or brittle fracture in service. Therefore, it is necessary to carry out post-weld heat treatments (PWHT) to reduce the level of residual stresses and transform the fresh martensite in the HAZ into softer and tougher tempered martensite. PWHT of Pelton or Francis hydraulic runners is costly due to the large dimensions and weights of these components, in addition to the logistical challenges associated with disassembly, transportation, and the consequence loss of revenue. When weld repairs are minor, the costs of PWHT become economically unfeasible. As an alternative, localized PWHTs (not global) can be performed on-site with appropriate equipment. However, doubts persist regarding how to verify the effectiveness of such localized PWHT. To ensure that these localized PWHTs achieve, at least, the improvement of the microstructure of the weld metal and the HAZ, hardness measurements can be carried out on-site and metallography can be performed in the field using the non-destructive technique of metallographic replicas. This work describes the methodology used to validate a procedure for acquiring and evaluating metallographic replicas on CA6NM steels and surfacing welds applied with EC410NiMo electrode under the following conditions: as-welded, with quenching, and quenching and tempering. The microstructures obtained with conventional laboratory metallography methods for AISI 4140 steel and EC410NiMo welds were compared with the replicas to establish the effectiveness of the technique for applications in hydroelectric turbine generator components. The procedure proposed by the study allows obtaining replica micrographs on CA6NM steel or similar welds with EC410NiMo of sufficient quality to identify the main constituents.

Experimental study of an energy dissipater for debris flow avalanches

2024-11-24T02:04:57+00:00

The research aims to evaluate a rigid energy-dissipating device under debris and hyper-concentrated flow conditions. The experimental development is carried out using a scale model using geometric, kinematic, and dynamic similarity conditions, using a channel of 2.3 m length, 0.7 m base, and 0. 07 m height, varying the slope between 2% and 8%, evaluated without device and with dissipating device, in this the separation of 14mm and 8mm grating bars is evaluated, arranging two structures separated at 0.4 m from each other along the study area, with an inlet flow of 0.015 m³/s and an average particle diameter of 5.1 mm. The experimental development shows a reduction of between 50% and 70% of the volume of debris flow in extreme conditions of channel slope (8%); likewise, a reduction of up to 93% is observed for slopes of 2% and up to 88% for slopes of 8% after the arrangement of the rigid energy dissipater. It is observed that in tropical zones the avalanche flow that presents the highest incidence is that of debris, which is a determining factor in selecting the alternative and dimensions of the type of energy dissipater; likewise, a representative positive impact is observed in the reduction of the impact after the arrangement of the dissipator, which indicates that this is a viable alternative to dissipate the energy of debris and hyper-concentrated avalanche flows in tropical zones, close to mountainous areas with slopes greater than 2.5%.

Cost of Capital and Return on Assets of Commercial Micro, Small, And Medium Enterprises (MSMEs) in Bogotá

2024-11-21T16:51:34+00:00

This study aims to analyze the cost of capital and asset returns among MSMEs in Bogotá's commercial sector from 2011 to 2021. The objective is to establish a foundation for financial decision-making, both retrospectively—evaluating if profitability during the study period was adequate—and prospectively, by assessing the financial viability of future investment projects. The research draws on theoretical concepts related to the cost of capital and return on assets, employing the Weighted Average Cost of Capital (WACC) to determine capital costs and the Capital Asset Pricing Model (CAPM) for equity costs. Asset profitability is measured using pre-tax operating profit and operating assets. This quantitative study examines a sample of 362 commercial MSMEs in Bogotá, excluding microenterprises, with findings indicating an average annual capital cost of 11.6% and an asset return of 7.8%. Notably, only in 2021 did asset profitability surpass capital costs.

A brief solution to three-body problem: Newtonian and Hamiltonian versions

2025-02-19T03:27:26+00:00

The problem of the three bodies was cataloged as one of the best-positioned problems and the pinnacle of functional analysis by Poincaré himself when he discovered that the problem itself presents a chaotic behavior and that it was impossible to apply integrable methods to this system. Therefore, its analytical solution was impossible to obtain, since its solution strongly depended on the initial conditions (weak chaos). With the development of modern numerical methods, together with the immense advances in the hardware of the new computers, attempts have been made to attack this system from different schemes and numerical stencils, to describe the main physical properties of this system (the trajectory is only one of these). With this, in the present work, we will study this problem from the Newtonian and Hamiltonian versions and the restricted problem. Special interest will be devoted to the numerical analysis of this system, The work focuses on a pedagogical description of the topic (constructivist), academic clarity, and application of numerical analysis.

Evaluation of the influence of rapid drawdown in some Colombian earth dam systems and reservoir zones through numerical modeling

2024-11-24T02:42:02+00:00

Rapid drawdown occurs when the reservoir level drops at such a rate that the material that makes up the slopes surrounding the reservoir or body of the dam is incapable of adequately dissipating the pore pressure. The numerical study of this phenomenon's influence becomes relevant to determine the effect of the variables and provide recommendations for a possible eventuality or the design of future projects. Using the GeoStudio 2012 software, this phenomenon was evaluated using numerical modeling by the simple and coupled analysis of two dams and three existing reservoir areas in Colombia. These structures were subjected to five emptying rates and four cases of drawdown levels. Parametric curves were obtained that represented the behavior of the safety factor in which a height of 2/3 of the normal level resulted in the most significant condition. Additionally, it was determined that the most critical situation corresponds to the day of or the one immediately following the end of the water drop. The simple analysis was greatly affected by the alteration of the conditions and characteristics of the dam soil. Conversely, the coupled analysis was greatly impacted by the drawdown level above the rate. These results made it possible to obtain the intervals of reduction percentages that the safety factor can suffer depending on the drawdown level.

Calibration of the Torrentiality Index for Extreme Flow Estimation in the Northwestern Andean Region of Colombia

2024-11-24T01:54:41+00:00

The estimation of extreme flows in a watershed is essential for risk and disaster management, the design of hydraulic structures and land use planning. The modified rational method of Témez, used to estimate peak flows, considers a torrentiality index that varies according to the geographical area. In Spain, there is an isoline map with index values between 8 and 12, while in the Colombian Andean region a general value of 11 has been used in several consulting studies. The objective of this study is to calibrate the torrentiality index in basins of the northwestern zone of Colombian Andean region, which includes the departments: Antioquia, Quindío, Caldas, Risaralda, Tolima and Huila. The methodology consisted of collecting and analyzing historical hydrometeorological data with records longer than 15 years from limnigraphic, limnimetric and precipitation stations of the Institute of Hydrology, Meteorology and Environmental Studies (IDEAM). Normal, Log normal, Gumbel and Log Pearson probability distribution functions (PDF) were applied. The selection of the PDF was made using the Kolmogorov-Smirnov test, which was used to estimate rainfall for the return periods of 10, 50, 100 and 200 years, and to obtain the mean daily intensity values (I_d). Also, intensity-duration-frequency curves were prepared, and hourly intensity values (I₁) were estimated for the different return periods. Subsequently, the torrentiality index equation (I₁/I_d) was applied, obtaining values between 9.7 and 15.5. The isoline map of the torrentiality index in the studied area was generated by means of a geostatistical analysis and spatial interpolation using Ordinary Kriging. This map allows the determination of the specific torrentiality index for each basin, applicable in the modified rational method. The validation of the observed and simulated flows shows a Nash-Sutcliffe efficiency between 0.77 and 0.95, indicating high acceptability of the errors of the objective functions.

Methodology for Generating Solid Three-Dimensional Models from Computed Tomography Using Academic and Open-Source Software

2025-02-12T20:36:44+00:00

The integration of image processing techniques for the generation of three-dimensional biomodels has driven significant advancements in biomedical engineering. These models have key applications in numerical simulations, such as those based on the finite element method allowing detailed evaluation of mechanical and biological environments, as well as the prediction of tissue structural behavior. This article presents a methodological approach to transform medical images into three-dimensional solid models using open-access or academic software, enhancing their applicability in educational and research contexts. The procedure is structured into three main stages: volumetric model generation from DICOM files, model editing and conversion into a solid and basic numerical analysis. Five different approaches were evaluated based on criteria such as number of required steps, process complexity, processing time, computational resource demands, reliance on additional tools, program limitations, and ease of preprocessing for subsequent simulations. From the comparison, it was identified that the combination of 3D Slicer for biomodel generation and Fusion 360 for editing, solid conversion, and numerical preprocessing is the most efficient and accessible alternative. The relevance of this methodology lies in its ability to serve as an essential preliminary step for computational numerical studies focused on areas such as tissue mechanics, biomechanics, and orthopedics. By enabling the generation of precise and adaptable models, this tool facilitates the evaluation of the structural and mechanical behavior of tissues based on the FEM. Consequently, the proposed enhances research and the development of personalized solutions in clinical and academic applications. This approach minimizes reliance on complementary tools.

Cyanotoxin degradation evaluation through low frequency ultrasound

2025-02-12T20:07:41+00:00

Cyanotoxins, such as microcystins (MC) and nodularins (NOD), are highly stable and resistant to conventional physical and chemical degradation, posing a significant risk to human health. In the present work, low frequency ultrasound was used as an advanced oxidation process to degrade cyanotoxins from a Colombian reservoir, evaluating the efficiency of the sonication process, using different powers (10, 30 and 50 W) and exposure times (5, 10, 20 and 30 min) under a frequency of 40 kHz. Ultrasonication proved to be ineffective for MC-LR concentrations up to 2595.42 μg/L, as no significant degradation was observed after 30 minutes of treatment. Additionally, a notable difference was evident in the concentrations of cyanotoxins in the water between sampling campaigns. Thus, risk assessment, implementation of monitoring programs and mitigation efforts in reservoirs deserve greater attention.

Kinematic calibration of serial robots using low-cost tools

2025-01-31T13:27:21+00:00

This paper presents the kinematic calibration of an open-chain robot using low-cost tools to measure the position of its end-effector. These tools include a smartphone video camera and an open-access online video analysis program. The methodology involves developing the robot’s direct kinematic and identification models, executing motion trajectories, and recording them in two perpendicular planes. The videos extract the kinematic position variables required for the identification model. This section explains the calibration process, including axis alignment, reference points, and length measurements. It also details how the position variables can be obtained either manually or automatically using the video analysis program. Next, the dimensions of the robot’s links are identified and validated by applying the calibrated dimensions to a trajectory different from the one used during calibration. When applied to an simulated ABB IRB120 robot, this methodology successfully identified the link dimensions with low errors. However, the precision achieved exceeded the specifications provided in the robot’s catalog. The use of the video analysis program allowed for the automated determination of the robot’s end-effector positions, significantly reducing human intervention in the calibration process. The proposed methodology is simple, cost-effective, and suitable for systems that do not require high precision.