Volume 62, Issue 7

The aim of this research is to study and evaluate the effects of cobalt and nickel additions on heat-treated and thermal-exposed microstructures in cast nickel-base superalloy grades based on GTD-111 with cobalt and nickel modifications. In the study, 1 wt.-% aluminium, as well as various cobalt and nickel contents, was added to all the modified alloy. After standard heat treatment, it was found that increasing the 1 wt.-% aluminium content affected the morphology of gamma prime particles, causing them to become more cuboidal in shape and larger in size. On the other hand, the size of gamma prime in all modified alloys decreased slightly with increasing cobalt contents. However, cobalt and nickel additions did not strongly affect the shape of the gamma prime particles. After long-term exposure at temperatures of 1173 K and 1273 K for 1440 ks, these gamma prime particles were much larger in size than those of heat-treated ones. The higher temperature caused extreme increases in the average size of thermal-exposed gamma prime particles. Also, the gamma prime particles became nearly spherical in shape and had lower coarsening rate with higher cobalt and lower nickel contents. Moreover, the addition of cobalt reduced the coalescence of gamma prime particles. Samples with cobalt content higher than 13.1 wt.-% were able to maintain the cubic shape of the particles even after long-term exposure at a temperature of 1273 K for 1440 ks. No topologically close-packed phase was found in any analyzed specimens.

Twist beam suspension systems are usually used in middle segment vehicles due to certain advantages. Researchers have presented many studies on both lightweight and functional twist beam design. In this paper, an optimization study is presented for enhancing the conceptual design of the twist beam by defining design variables along the twist beam as subject to vehicle handling conditions.Toe and camber angles are essential parameters that determine vehicle behavior during maneuvering. In this study, opposite wheel travel analysis is performed to represent maneuvering behavior. Therefore, while the optimization study is presented in the form of weight reduction, it is aimed to keep the toe and camber angles at certain intervals. Ant lion optimizer and mothflame optimization methods, which are population-based optimization methods, are used in the optimization phase to evaluate the performance of the new algorithms as compared with genetic algorithm in terms of robustness and correctness in the case of twist beam design. A two stage approach is introduced for presenting the optimization model and analysis. In the first stage, design space is created via the Latin hypercube method; the mathematical model is obtained via the least squares regression method. Finally, the mathematical model is solved to enhance twist beam conceptual design using recently developed population based optimization algorithms.

High-entropy alloy composites were fabricated by ball milling, cold isostatic pressing and microwave sintering to which were added varied contents of Al 2 O 3 whiskers, La-Ce, and carbon nanotubes-graphene, respectively. The structure and mechanical properties of the composites were investigated by X-ray diffraction, scanning electron microscopy and a microhardness tester. The high-entropy alloy and composites show amorphous phases and some crystalline phases. Accordingly, the addition of the reinforcement phase can refine the grain size. The formation mechanism of the phase is mainly related to the factors of mixing entropy, enthalpy, differences in atomic size, and the structure and property of the elements. The hardness of the composites is higher than that of the alloy (437.5 HV), and those composites reinforced by 0.5 wt.-% nanotubes- 0.5 wt.-% graphene are the highest (593.99 HV). The fracture morphology of the Al 2 O 3 whisker reinforced composite shows a river pattern, indicating brittle cleavage. According to the research results, it can be concluded that the strengthening mechanism of the high entropy alloy composites mainly reflects fine grain strengthening and load transfer, and the toughening mechanism mainly crack bridging and a pulling out of the reinforcing phase.

Armor 500T steel used in armored military vehicles and marine vehicles were joined by CO 2 laser beam welding method by applying three welding powers and two welding speeds under shielding argon atmosphere. From microstructure and microhardness results, under low laser welding power and high welding traveling speeds, microstructural transformation in the joining region of the performed welds occurred at a narrower distance as compared to other parameters, and it was determined that four regions formed independent of each other for each parameter group. Furthermore, it was determined that there is a gradual decrease in the microharness values of samples in which welding parameters cause heat input to decrease. The fatigue test results of all samples showed high strength properties in the parameters with high heat input. Additionally, tensile test results for all samples with high heat input parameters also exhibited high strength properties. Fracture at the intersection at high heat input parameters of a relatively ductile separation type occurred in HAZ whereas, at other parameters fracture occurred at the weld center and wide gap semi-brittle fracture behavior was observed. As a consequence, it was found that the most effective parameter as compared with laser welding power is laser welding traveling speed.

Laser cladded NiCrBSi alloy coating was fabricated on the surface of a 42CrMo roll using a 6 kW fiber laser. The effects of the laser power, scanning speed and feeding rate on the cladding layer form, size, dilution rate, microstructure, and hardness of coating were studied by using optical microscopy (OM), scanning electron microscopy (SEM) and a microhardness tester. The results show that the microstructure, size, dilution rate and hardness of the cladding layer had changed with an increase in laser power, powder feeding rate and scanning speed. The appropriate parameters of the laser cladding experiment are as follows: the laser power is 2000 W, powder feed rate 20 g × min-1, the scanning speed 4 mm × s -1 . The cladding layer and the substrate exhibit good metallurgical bonding under the above processing parameters. The microstructure of the cladding layer is fine, the dilution rate is 9.8 wt.-%, and the microhardness of the cladding layer is 710.7 HV.

In the normal operation of a spherical robot, its spherical shell structure is often accompanied by low velocity impact. At the same time, the spherical shell structure should take into account its protective ability against high strength impact of small probability. Glass fiber reinforced polymer (GFRP), which has high specific strength, specific stiffness, corrosion resistance and an impact energy dissipation coefficient, can be used as the ideal spherical shell material for spherical robots. In this study, the low velocity impact damage of GFRP spherical shell is studied based on the background that a thin-walled shell structure of spherical robot may suffer from large deformation and dynamic load. This study is divided into three aspects: experiment, simulation and calculation. The dynamic response and residual bearing capacity of the GFRP spherical shell is obtained through experiments; the progressive damage model of the composite structure, which demonstrates expounded stress distribution, a structural deformation mode and an energy dissipation mechanism under impact, is established based on the Hashin criterion. Low velocity impact-penetrating failure of the elastic brittle thin-walled GFRP spherical shell is calculated according to the geometrical principle and energy method. In this paper, the material dynamic behavior and impact damage of a GFRP spherical shell are systematically studied. This is of great significance for the development of high-performance spherical robots and the realization of accurate control.

The purpose of this experiment was to prepare high-voltage porcelain ceramics as local raw materials. Density, water absorption, and volume shrinkage were determined according to the State standard (GOST 7025-91). A structural analysis was carried out using a scanning electron microscope, and an X-ray phase analysis was carried out on an Xpert PRO diffractometer. It was found, that in the initial state, ceramics consist of hexagonal (SiO 2 ) and a small amount of monoclinic phase. Above a temperature of 1150 °С they consist of hexagonal (SiO 2 ), an orthorhombic lattice, and also contain mullite (Al 2 Si 2 O 13 ).

Conventionally cast Alloy 247 LC is characterized by good creep rupture strength and corrosion resistance at high temperatures and is therefore frequently used for cast components in the aero-engine and power generation industries. From a welding technology point of view, the precipitation- hardening nickel-based alloy has an increased susceptibility to hot cracking. Due to its high segregation tendency and its γ’ precipitation formation, the material is even classified as non-weldable. However, electron beam welding in a vacuum as the method of choice for joining and repairing nickel-based components in industrial practice, provides a variable beam welding process with high energy density. This allows varied temperature gradients to be implemented. In this paper, results of welding parameter optimization with regard to hot crack reduction are presented. For this purpose, a comprehensive crack analysis was carried out using scanning electron microscopy, metallography and X-ray microtomography and was then compared with the temperature gradient along the fusion line. Two hot cracking phenomena were identified and differentiated. Thereby, a clear dependence between temperature gradient and crack reduction becomes obvious.

This paper presents the effect of additives on the quality of a product created by 3D print. The product is created by the most widely used 3D printing method - Fused Deposition Modeling (FDM). Polylactic acid (PLA) filaments are tested without and with the addition of carbon fibers or copper. The specimens are characterized by different methods, such as mechanical testing, measuring roughness by digital microscope with a large depth of field and thermal analysis. In fact, FDM is a problematic process with numerous criterions that affect printing quality. Printing parameters such as print temperature, pad temperature, print speed for 3D printing, printing orientation etc. have an important impact on the performance and quality of FDM components. Due to the correct parameters, the product of the required quality with a longer service life is obtained. The results of testing show that the quantity and choice of the right ingredient has a major impact on the mechanical properties and overall quality of the investigated product.

In this study, B 4 C and FeCrC powders were alloyed on the surface of AISI 430 by a fusion process via plasma transferred arc welding. Mixtures of these powders at various amounts were used. The microstructure and wear behavior of the obtained coating layers were investigated. The wear behavior of the coating layers was planned using the Taguchi method. Abrasive wear mass loss results were optimized with the “smaller the better” control characteristic of the Taguchi method, and the results were analyzed graphically. The actual data obtained at the end of the study were formed by using an L 16 (4 × 2, 2 × 2) mixed array, and the remaining wear rates were calculated with the help of theoretical formulas in order to obtain theoretical abrasive wear results.

Resistance spot welding is an extensively used production process in the industry. The joint strength of sheet metal parts bonded by resistance spot welding is expected to be sufficient. Furthermore, it is desirable that the appearance of the welding area be acceptable on visible surfaces. In regard to having an adequate surface appearance on the welded area, is necessary to remove the color changes on the unpainted surfaces and to eliminate the indentations caused by the welding pressure. In this study, an objective evaluation was performed using the color measurements of the test samples joined with resistance spot welding. The effects of welding parameters on surface appearance were investigated and the most suitable settings for the appearance of the welded surface were discussed.

In this paper, the sine-cosine optimization algorithm (SCO) is used to solve the shape optimization of a vehicle clutch lever. The design problem is posed for the shape optimization of a clutch lever with a mass objective function and a stress constraint. Actual function evaluations are based on finite element analysis, while the response surface method is used to obtain the equations for objective and constraint functions. Recent optimization techniques such as the salp swarm algorithm, grasshopper optimization algorithm, and sine-cosine algorithm are used for shape optimization. The results show the ability of the sine-cosine optimization algorithm to optimize automobile components in the industry.

This paper deals with the electromechanical actuator (EAct) design for a seat latch while maintaining required force and displacement according to the boundary conditions and design criteria for the finite element method (FEM) in an Ansys Maxwell environment. Before presenting the analysis studies, some EAct models are parameterized according to the Taguchi’s design of experiment (DoE) method. After that, analysis results are evaluated to define the critical model parameters of the EAct according to the DoE method. Furthermore, the DoE results and design parameters of the EAct are trained in some cases by an artificial neural network (ANN). The dynamic behavior of the models from the ANN and DoE results are analyzed and the results obtained are compared. Finally, the optimal EAct model is defined taking into account design criteria.

In this study, the production and analysis of a composite vessel were performed. The materials selected for the design of the composite materials were glass fiber/epoxy, carbon fiber/epoxy and Kevlar fiber/epoxy material. Anti-symmetric orientation angles of (30°-30°), (45°-45°), (60°-60°) and (75°-75°) were used for each material. In the design of the vessel, the total thickness of the wall is defined as 3 mm. The containers were modeled using the SOLIDWORKS package program with the wall thickness of 10 and 20 layers. The containers modeled are then analyzed to determine maximum deformation and maximum stress by using the ANSYS WORKBENCH 14.0 package program which analyzes according to the finite element method. While making solutions, a pressure of 1.65 MPa as the test pressure of the vessel was defined as hydrostatic from the inner surface of the vessel, and von-Mises stress and total deformations were determined. As a result of this study, it has been determined that a 60°-60° orientation angle is the most appropriate design angle considering both the deformation values and maximum stress. Maximum stress in the design of composite containers was far below the flow limit and remained within acceptable limits for shape changes.