Misan Journal of Engineering Sciences

A New Theory of Damage Estimation and Fatigue Life Prediction

Jasim H. AL-Bedhany, Stanisław LEGUTKO, Ali Al-Maliki, Tahseen Ali Mankhi — Thu, 21 Dec 2023 00:00:00 +0000

There are a considerable number of fatigue damage estimation theories and fatigue life prediction of mechanical components. The most popular one is Palmgren-Minor (P-M) theory. This theory has been used in the standards for selecting the bearing –as a component subject to fatigue loading- and for expecting the bearings lives. In Wind Turbine Gearboxes (WTGs), the bearings were selected to be without maintenance for 20 to 25 years; however, in real service life, the bearing suffer from premature failure within a life span of quite less than the design life (1 to 5 years). A new applicable methodology and a procedure of calculation for damage estimation due to fatigue loading and predicting the life has been suggested and tested. Results of 20 rolling and sliding tests which conducted under severe contact loading are used to test this method. The suggested method depends on calculating the number of operating cycles under a specific contact loading level to an equivalent number of loading cycles under the average loading level. This method depends on the area under the S-N curve without any correction or loading factors and can be used to predict the WTG bearings failure to manage the maintenance because the current life prediction standards have very high percentages of error (> 400%). The reliability of this approach can be further verified by utilizing actual operational data from Supervisory Control and Data Acquisition (SCADA), used for overseeing wind turbine operations. Additional examinations are necessary to confirm the dependability of this novel method.

Comparative Analysis of GA-PRM Algorithm Performance in Simulation and Real-World Robotics Applications

Sarah Sabeeh, , Israa S. Al-Furati — Thu, 21 Dec 2023 00:00:00 +0000

Abstract: This paper presents a comprehensive analysis of the performance of the Genetic Algorithm Probabilistic Roadmap (GA-PRM) algorithm in both simulated and real-world robotic environments. The GA-PRM algorithm is a promising approach for robot path planning, and understanding its behavior in different settings is crucial for its practical applications. In simulations, we explore the advantages of controlled and reproducible test conditions, allowing for extensive parameter tuning and algorithm improvement. Real-world testing is employed to validate the algorithm's performance in actual robotic environments, taking into account the inherent complexities and uncertainties present. In our comparative analysis, we found that the GA-PRM algorithm demonstrates significant improvements in real-world scenarios compared to simulations. Specifically, the algorithm produced shorter paths in real-world robot testing, with an average length of 21.428 cm, as opposed to 25.6235 units in simulations. Moreover, the computational efficiency of the algorithm was notably enhanced in the real-world environment, where it took only 0.375 seconds on average to plan paths, compared to 0.6881 seconds in simulations. The algorithm also exhibited higher path smoothness in the real world, with an average smoothness score of 0.432, compared to 0.3133 in simulations. These results underscore the algorithm's adaptability to real-world conditions and its potential for efficient navigation in practical healthcare and automation applications. Our research bridges the gap between simulation and reality, facilitating the development of more reliable and adaptable robotic systems. The insights gained from this comparative evaluation contribute to a deeper understanding of the GA-PRM algorithm's behavior and its potentials.

Enhancing Seismic Performance of Multi-story Steel Buildings Using Inner Mega Braced Frames

Ayman zaki Abdulhameed — Thu, 21 Dec 2023 00:00:00 +0000

damage to buildings. In this study, a multi-story steel building is designed using the ETABS v16 software under vertical loads only. Subsequently, seismic performance was enhanced by employing five different Mega braced frames (MBFs) systems in two cases: in the first case, the five bracing systems are placed within a frame located 6 meters away from the outer frame, while in the second case; the bracing systems were placed within a frame located 12 meters away from the outer frame. The building was then analyzed using nonlinear time history analysis with SAP 2000 V20 software, utilizing seismic data from the El-Centro earthquake available in SAP 2000 V20. The results were compared based on various parameters such as maximum roof displacement, maximum inter-story drift ratio, and maximum base shear. The findings demonstrated an improvement in the building's response, in the first case maximum roof displacement reduction ranging from 36.08% to 48.29% in both directions, and from 36% to 44% for maximum roof displacement in the second case. Maximum inter story- drift ratio also reduced by percentages ranging from 25% to 46% in the first case and 25% to 39% in the second case. From the analysis results, it is evident that the best pattern in the first case is pattern5, while in the second case pattern4 is the best.

Improvement of Concrete Mechanical Properties by Adding Nanomaterials

Thu, 21 Dec 2023 00:00:00 +0000

This study examined the impact of replacing the cement weight in concrete with nanomaterials (mix (C) 1% Carbon Nanotube CNT, mix (T) 2.5% Nano Titanium and mix (S) 3% Nano Silica) on the concrete mechanical properties through experimental investigations and comparison with normal concrete to show the extent of the effect of adding nanomaterials on the properties of concrete. The differences and increasing in the compressive strength for the mix (T) by comparison with the mix (N) and the mix (S) in the age of 7 days the increasing was 17% and 80% for the mix (S) and (T) respectively, In the age of 28 days the increasing was 44% and 60% with the mix (S) and (T) respectively and in the age of 56 days the increasing was 32% and 36% with the mix (S) and (T) respectively. The compressive strength for mix (C) was decreased 39%, 22%, 13% compared with the compressive strength for mix (N) at 7, 28 and 56days, respectively. The best improvements in compressive strength and splitting tensile strength for the mix that was added Nano Titanium (T) replacement by (2.5%) from weight of cement. For the mixes with nano material, a highest unit weight was observed at the age of 28 days. Referring to the results of SEM (Scanning electron microscope), the effect of nano Silica on the durability and mechanical properties of concrete can be explained by microstructure and from measuring X-ray diffraction (XRD) of concrete samples with the added Nano materials, these materials added to the concrete have clearly affected on the crystalline and chemical structure of the cement mortar components.

Experimental and Numerical Study of Torsional Solid and Hollow Section of Polyolefin Fiber-Reinforced Concrete Beams

Iman H. Majeed — Fri, 22 Dec 2023 00:00:00 +0000

An experimental and theoretical program was undertaken to enhance comprehension regarding how variations in fiber ratio impact the structural performance of both solid and hollow reinforced concrete beams when subjected to pure torsion. Polyolefin fiber was utilized in this study. To achieve this objective, a total of sixteen specimens of fiber-reinforced concrete beams were manufactured. Among these, eight were solid beams, while the remaining eight were hollow beams, all featuring rectangular cross-sections. These specimens were constructed employing polyolefin fiber. The findings indicated that incorporating polyolefin fiber into the concrete mixture led to improved mechanical properties in the cured concrete. The most significant enhancements were observed in the splitting tensile strength and flexural strength tests conducted on the specimens. Both solid and hollow beams exhibited notable enhancements in their torsional performance. These enhancements occurred as the polyolefin fiber percentage increased from zero to 1.5%, while the transverse and longitudinal reinforcement ratios remained constant. Furthermore, the reduction ratio of torsional strength becomes more noticeable when comparing solid and hollow sections in high-strength beams, as opposed to normal-strength beams.

An Experimental Study on Modified Concrete Using Partial Replacement of Gravel and Admixtures

Yousif Jabbar Lafta, Muthana Sh. Mahdi, Adel Al Menhosh, Hussein Ali H. Algusab — Wed, 27 Dec 2023 00:00:00 +0000

Abstract: This study aims to test a concrete specimen with replacement partially of 15 % of the coarse aggregate by pieces of tires and volcanic aggregates and reduce 5% of the water/cement ratio by substituting with 4% percentages of styrene butadiene rubber (SBR) and 1% of superplasticizer. The main concrete components (cement: sand: gravel) were used in weight ratios (1:1.5:3) and a water to cement 0.45 was used and it was considered as a reference sample (Mix1). A water to cement ratio 0.40 was depended for the modified mixtures. Samples were cast for testing the compression strength with sizes 150 ×150 ×150 mm for ages 7 and 28 days. the absorption rate, with a size of 100 ×100 ×100 mm at age 28 days. Moreover, 150 ×150×150 mm for depth of penetration test at the age of 28 days.

Briefly, the observed results were exhibited that the partial replacement of normal aggregate in concrete with volcanic aggregate affects negatively on the workability, so 4% of the polymer SBR and 1% of the superplasticizer have improved the workability. The improvement in the workability of concrete contributed to reducing the ratio of water to cement required for mixing compared to ordinary concrete, and this in turn led to an improvement in performance of hardened concrete. In addition, the reduction of the permeability level. The results also illustrated that the replacement of the gravel in the modified mixtures (Mix 3 and Mix 2) reduces the weight of hardened concrete by (10-12%) and (7-9%) compared with conventional concrete, respectively, which makes it suitable for use in mediumweight concrete applications.

Moreover, it can be concluded that the strength properties of the modified mix with volcanic aggregate improved by 19-20% compared to that of the unmodified concrete. While the modified concrete by cutting tires showed significant deterioration in the concrete's resistance 21% despite the reduction of concrete permeability.