Volume 63, Issue 5

Polylactic acid (PLA) is a commonly used biodegradable material in medical and increasingly in industrial applications. These materials are often exposed to various flaws and faults due to working and production conditions, and increasing the demand for PLA for various applications requires a full understanding of its fracture behavior. In addition to ABS, PLA is a widely used polymeric material in 3D printing. The gyroid type of filling is advantageous for overcoming the relatively higher brittleness of PLA in comparison with conventional thermoplastic polymers. In this study, the effects of various filling ratios on the fracture toughness of 3D printed PLA samples with gyroid pattern were investigated numerically and experimentally for pure mode I, combined mode I/II, and pure mode II. Two-dimensional finite element modeling was created, and the two-dimensional functions of stress intensity coefficients were extracted in loading mode I, mode I/II, and mode II at varied filling ratios of the gyroid PLA samples. Mixed-mode fracture tests for 3D printed PLA samples with a gyroid pattern at various filling ratios were performed by using a specially developed fracture testing fixture. The results showed that the amount of fracture toughness of the samples under study in tensile mode was much higher than those values in shear mode. Also, as the percentages of the filling ratios in the samples increased, both tensile and shear fracture toughness improved.

Cutting forces play a significant role in machining because they directly affect the mechanics of machining, the energy requirements, and the tool stability required. In this study, the cutting forces occurring during the turning of AISI 4340 material with 30 Rockwell C hardness scale have been analyzed both experimentally and numerically. Many types of research have been conducted via 2-D simulation using the finite element analysis method. In other words, in most studies, the workpiece was modeled as a flat specimen. Therefore, this paper presents a real 3-D turning simulation model using cylindrical specimens. The cutting forces were measured using a Kistler 9129AA model piezoelectric dynamometer. The ABAQUS/Explicit finite element method was used, and a model by Johnson and Cook was assigned as a material model in the numerical analysis. A new PVD AlTiN coated carbide insert was incorporated to prevent wear. Experimental results obtained from cutting tests were compared with numerical results to establish the accuracy of the FEM. It was observed that experimental and numerical results overlapped each other. Thus, this method can be used directly in the industry to reduce high processing costs.

In this research, composite parts joined according to different joining methods such as single-lap and double-lap embedded adhesive subjected to tensile load were analyzed via the 3-D finite element method (FEM). The study differed from other studies in terms of joining techniques used and the specified parameter and model design. This study aims to emphasize the advantages of joining techniques in terms of aesthetically and joining methods over each other. In the analysis, composite parts carbon/epoxy (T 700) at varied fiber orientation angles and adhesive DP 410 were used. The models for numerical analyses were created in an ANSYS 14.5 software package. Finite element analysis (FEA) was successful in predicting failure loads. Stress in the x, y, z directions, shear stress and von-Mises stress on the adhesive were obtained at the time of failure for predetermined parameters. As a result, the effects of orientation angles, overlap lengths, adhesive layer and bonding methods were investigated. The maximum effect parameter and joining technique was determined for the composite parts joined through varied joining methods.

Grade 2, the most widely used pure titanium in the industry, has high corrosion resistance, excellent ductility, good weldability and is easily machinable. If titanium is exposed to temperatures above 500 °C due to moisture or hydrocarbons in the air, it is susceptible to taking up oxygen, nitrogen, carbon and hydrogen. This can cause cracks, especially after welding. Therefore, protection of the welding zone from external factors is of great importance during welding. For these reasons, TIG welding is the most widely used method for titanium welding. In this study, Grade 2 pure titanium plates are joined by TIG welding at three (40 A, 60 A and 80 A) current values under the same conditions. For the welding process, 2 wt.-% cerium addition Tungsten tip and high purity (99.99 vol.-%) argon was used as a shielding gas. After a visual inspection of the welded samples, microstructure inspections, macrostructure inspections, hardness measurements, bending tests and tensile tests were performed in accordance with the standards. As a result of the investigations, it was determined that the most suitable current value for the joining of Grade 2 titanium by TIG welding was 60 A.

In Inconel 783 alloy, there are mainly two kinds of strengthening phases of β and γ’. In addition, it is found that there are other precipitated phases in the alloy’s β phase. By means of multiple testing methods, the types and functions of the precipitated phase in the β phase were determined. The results showed that the precipitated phases from β phase were nanoscale Nb and Ti carbides and a large number of white needle-like Laves phases. The former, due to its small size, which can improve the grain boundary slip resistance of the alloy, thus improves the shaping of the material. While the latter, due to its sharp shape and due to its large amount, destroys the original structure of the β phase and greatly reduces the room temperature plasticity of the alloy.

Today, fluid transportation via pipes can be found in many sectors. Therefore, safe fluid transportation possesses critical importance. While working, transportation pipes are exposed to unwanted loads that culminate in stresses which cause deformation on the part geometry especially in sharp corners, holes or sudden cross-section change areas considered as notched. The notch effect parameter is considered in the mechanical design formulas. This study is interested in the notch factor that is estimated for a cylinder which undergoes an inner pressure. Some users can use false numerical values due to misreading or lack of attention. Because of this reason, graphs were converted to the numerical value by using computer software. In this study, Peterson’s chart was accepted as scientifically valid. Stress concentration factors were obtained by using four other approaches. These are regression, analytical, artificial neural network and finite element analysis. Among these models, high accuracy values were given by the artificial neural network model.

Stress intensity factors numerically investigated the Mode I loading of composite plates with an edge crack and repaired with a patch on a single side. The effect of the fiber orientation angle for both composite plate and the patch were analyzed with regard to crack length, adhesive properties, and plate thickness. The stress intensity factors were calculated by using the quarter point element that can be applied to 3D crack problems of homogeneous anisotropic materials.It was observed in this study that the fiber orientation angle affects the stress intensity factors significantly.

Metaheuristic optimization algorithms have gained relevance and have effectively been investigated for solving complex real design problems in diverse fields of science and engineering. In this paper, a recent meta-heuristic approach inspired by human social concepts, namely the queuing search algorithm (QSA), is implemented for the first time to optimize the main parameters of the spur gear, in particular, to minimize the weight of a single-stage spur gear. The effectiveness of the algorithm introduced is examined in two steps. First, the algorithm used is compared with descriptions in previous studies and indicates that the final results obtained by QSA lead to a reduction in gear weight by 7.5 %. Furthermore, the outcomes obtained are compared with those for the other five algorithms. The results reveal that the QSA outperforms the techniques with which it is compared such as the sine-cosine optimization algorithm, the ant lion optimization algorithm, the interior search algorithm, the teaching-learning-based algorithm, and the jaya algorithm in terms of robustness, success rate, and convergence capability.

This paper focuses on a comparision of recent algorithms such as the arithmetic optimization algorithm, the slime mold optimization algorithm, the marine predators algorithm, and the salp swarm algorithm. The slime mold algorithm (SMA) is a recent optimization algorithm. In order to strengthen its exploitation and exploration abilities, in this paper, a new hybrid slime mold algorithm-simulated annealing algorithm (HSMA-SA) has been applied to structural engineering design problems. As a result of the rules and practices that have become mandatory for fuel emissions by international organizations and governments, there is increasing interest in the design of vehicles with minimized fuel emissions. Many scientific studies have been conducted on the use of metaheuristic methods for the optimum design of vehicle components, especially for reducing vehicle weight. With the inspiration obtained from the above-mentioned methods, the HSMA-SA has been studied to solve the shape optimization of a design case to prove how the HSMA-SA can be used to solve shape optimization problems. The HSMA-SA provides better results as an arithmetic optimization algorithm than the slime mold optimization algorithm, the marine predators algorithm, and the salp swarm algorithm.

The marine predators optimization algorithm (MPA) is a recently developed nature-inspired algorithm. In this paper, the Nelder-Mead algorithm is utilized to improve the local exploitation powers of the MPA when described as a hybrid marine predators and Nelder-Mead (HMPANM). Due to the harsh competitive conditions as well as the transition to new vehicles such as hybrid and full-electrical cars, the interest in the design of light and low-cost vehicles is increasing. In this study, a recent metaheuristic addition, a hybrid marine predators optimization algorithm, is used to solve a structural design optimization problem to prove how the HMPANM can be used in solving industrial design problems. The results strongly prove the capability of the HMPANM for the optimum design of components in the automotive industry.

This paper investigates the use of rice straw powder in a brake pad as a substitute for asbestos which is a carcinogenic with detrimental effects on health. Rice straw powder was used as a novel material in a brake pad. Rice straw powder has a silica content which gives the pad a c eramic-like action. Rice straws were ground after drying in order to produce the powder. Five laboratory varieties were produced, altering the rice straw powder ingredients from 5, 10, 15, 20 and 25 wt.-%, respectively added to other abrasive materials, binder, friction modifiers, solid lubricant, and filler material utilizing conventional techniques. In this study, the friction surface temperature, the wear amount, and the change of the friction coefficient were determined. Additionally, the microstructure specifications of the brake pads were determined using scanning electron microscopy. Experimental results showed that a 15 wt.-% fraction of rice straw powder yielded better wear and thermo-mechanical features as compared with other combinations. The micro-structure shows a uniform distribution of the rice straw powder in the matrix. Hence, rice straw powder can be a possible candidate friction material for producing non-asbestos new brake pad without any detrimental impact.

Environmental pollution from various industries is a serious issue in most countries. Bagasse is a waste product from sugar factory industries. Bagasse pollutes the soil and the air. In the present investigation, an attempt has been made to utilize bagasse waste as a primary reinforcement material in the development of an aluminum-based metal matrix composite. Magnesium oxide (MgO) powder was mixed with bagasse ash to enhance the wettability of the bagasse ash and the aluminum matrix. The microstructure results of the bagasse reinforced hybrid composite showed a proper distribution of carbonized bagasse ash and MgO powder in the aluminum base matrix material. Minimum porosity and minimum corrosion loss were measured at 1.43 % and 0.05 mg, respectively for a selected composition Al+2.5 wt.-% carbonized bagasse ash +12.5 wt.-% MgO hybrid metal matrix composite. The composition of the Al+10 wt.-% carbonized bagasse ash metal matrix composite exhibited the maximum specific strength of 39.59 kN × m × kg-1 which is much better than than that of the base matrix material. In addition, as the percentage of reinforcement in the casting increases, the cost and density of the final cast composite reinforced by bagasse, continually decrease. Sample G 13 (Al+ 5 wt.-% carbonized bagasse ash + 10 wt.-% MgO powder) shows a small change in dimensions due to thermal expansion.

Reduction in wear of artificial bio-implants results in the release of a lesser amount of wear particles into the blood stream. This paper focuses on analyzing the tribological behavior of ceramic and polyethylene bio-materials experimentally. Four different biomaterials namely Zirconia, Silicon Nitride, UHMWPE (ultra high molecular weight polyethylene) and PEEK (polyether ether ketone) are investigated for friction and wear coefficients using a pin on disc (PoD) tribometer. Alumina (Al 2 O 3 ) is chosen as the disc material. Polyethylene based UHMWPE and PEEK are used as a pin material with the hemispherical end, while, Zirconia and Silicon Nitride ceramic materials are used in the form of spherical ball. 0.9 % NaCl (saline solution) is used as a lubricant medium. Zirconia showed a better reduction in friction and wear coefficient characteristics under lubrication conditions when compared with polyethylene and other ceramic materials. The estimated friction and wear coefficients would be helpful for surgeons and academicians to choose better wear-resistant bio-compatible materials for effectively design hip prosthesis. The present study compared the tribological behaviors of ceramic materials Si 3 N 4 and ZrO 2 and polyethylene materials PEEK and UHMWPE with a ceramic counterpart Al 2 O 3 disc. In the lubrication case, ZrO 2 showed a better reduction in friction and wear characteristics while in the dry case UHMWPE showed lesser wear characteristics.

With the gradual reduction of mineral resources, marine mining has increasingly been developed as a method of exploiting resources. However, the cutting efficiency of submarine mineral deposits requires additional improvement. Investigating the preferable cutting efficiency in marine mining, it is important to establish a theoretical model of predicting the peak cutting force for polymetallic sulfide. The polymetallic sulfide was taken from the floor of the Indian Ocean and maintained at constant temperature and humidity conditions during transportation. In the paper, some experiments were conducted to study the physicomechanical properties of polymetallic sulfide. And the cutting experiments were conducted to investigate the cutting force at room temperature and atmosphere pressure, preliminarily. Then, based on maximum tensile stress theory, the theoretical equation of predicting the peak cutting force was derived, and an improved high-precision theoretical model was established. The reliability and accuracy of this model was verified using the experimental data. Based on the improved theoretical model, the brittleness index and the cutting depth, which influenced the peak cutting force, were investigated. Results show that the established model improved the accuracy of predictions. The peak cutting force decreased with the increase of the brittleness index, but it increased with the increase of the depth, which followed the power-law pattern. The power-law coefficient was generally at 1-2. The experiments verified that this improved theoretical model and the related conclusions can predict the peak cutting force. It is significant for the design and study of conical picks and cutting mechanisms in marine mining.