Volume 63, Issue 10

A TC4 titanium alloy plate was lap joined to a 304 austenitic stainless steel plate via friction stir welding. The microstructures at the lap joint interface were intensively examined by means of energy dispersive X-ray spectroscopy and transmission electron microscopy analysis, and the mechanical properties of the lap joint were evaluated by a microhardness and shear tensile test. The results show swirling-like stir zones of TC4 and 304 SS are formed along the interface, where an aprox. 200 nm interface layer composed of TiFe and TiFe 2 intermetallic compound is dispersed at the high rotating speed of the tool. In addition, the high hardness value is discontinuous distribution at the interface, and the shear strength of the commercially TC4 plate and 304 SS FSW lap joint can reach 7507 N at a rotational speed of 600 rpm, a welding speed of 30 mm/min, and a press amount of 0.4 mm.

Inconel 625 alloy is used in aggressive environments at high temperatures such as in petro-chemical applications, in the aeronautical and nuclear energy industries because of its propitious mechanical properties and corrosion resistance. In this study, Inconel 625 samples were joined with ERNiCrMo-3 filler metal using the MIG (metal inert gas) method. Also, the relationship between the microstructure and corrosion properties of the Inconel 625 weld were investigated. The microstructure properties of the weld metal were determined by a light metal microscope (LMM), a scanning electron microscope (SEM) and by energy dispersive spectroscopy (EDS) analysis. Moreover, the corrosion properties of the weld metal and the base material were examined by potentiodynamic polarization tests. The corrosion behavior and parameters of the electrochemical potentiodynamic polarization were determined depending on microstructure properties. Inconel 625 was joined successfully via multipass welding. Moreover, excessive heat input ensured the formation of intermetallic phases. Mechanical and corrosion properties of the weld metal were affected negatively due to the formation of intermetallics.

The creep behavior of the babbitt alloy SnSb8Cu4 was studied by impression under constant stress in the range of 15-30 MPa and at temperatures in the range of 333-393 K. OM, XRD, and SEM technologies were used to investigate the microstructural evolution of the material before and after creep. In conclusion, the stress exponent of SnSb8Cu4 in impression condition is 2.7. The creep activation energy is 46.7 kJ × mol -1 , which reveals that the creep mechanism is based on dislocation glide controlled by dislocation pipe diffusion. With an increase in creep temperature and stress, the thermal vibration of the atom and atomic diffusion velocity increase. Moreover, Cu 6 Sn 5 phase cannot effectively hinder dislocation glide and strengthen the material in a condition of high creep temperature and high stress, thus resulting in the decrease of creep resistance. After creep, the grains are elongated along the deformation flow direction both near the pressure punch edge and in the hemispherical zone beneath the pressure punch. The most severe deformation zone is near the pressure punch edge, whereas, no detectable deformation is found in other areas. It is concluded that impression creep is a localized phenomenon.

Boriding or boronizing is a type of surface property improvement process applied to metal or some non-metal materials by diffusion. The calculation of diffusion kinetics is also very important as it is a diffusion controlled process. Today, many researchers perform kinetic calculations by applying the Second Fick’s law to the Arrhenius equation. In this study, as an alternative to conventional kinetic calculations, the mathematical modeling of diffusion kinetics has been performed using the integral diffusion model. For the boronizing experiments, the pack-boronizing method was chosen and AISI 316 austenitic stainless steel was used. The experiments were carried out at three temperatures and for three times; Ekabor 2 was used as the boronizing agent. The detailed diffusion kinetics calculations were made using the data obtained from the experiments in the mathematical modeling.

The Mode-I interlaminar fracture characteristics of aramid fabric andcarbon fabric reinforced epoxy composites along with the influence of SiC particle content were explored. Double cantilever beam (DCB) tests were performed in accordance with ASTM D 5528 for the purpose of examining the behavior of Mode-I delamination. The results showed that, the adhesion strength of an SiC particle within an aramid/ epoxy composite system was better than that within a carbon/epoxy composite system. The highest values of Mode-I fracture toughness of an aramid fabric/epoxy specimen and a carbon fabric/epoxy specimen were 1391 J × m -2 and 701 J × m -2 with SiC particle contents of 10 wt.-% and 5 wt.-%, respectively. The micrographs from optical and scanning electron microscopes verified the enhancements of Mode-I interlaminar fracture toughness behavior.

AISI type 430 stainless steel is a common current collector in sodium sulfur batteries. The corrosion behavior of stainless steel 430 (SS430) was investigated in this article in a sulfur environment at 350 °C using the gravimetric method. The corrosion mechanism and the characteristics of vulcanization films were studied by diffraction X-ray (XRD) and scanning electron microscopy (SEM), and resistance was tested by a four-probe tester. The results showed that the intensive vulcanization of SS430 took place at a corrosion time above 24 h. The dynamic vulcanization of SS430 first increased to a maximum point of 0.6532 mm × a -1 after 120 h in a 350 °C molten sulfur environment and then decreased. Block resistance reached 0.6058 m Ω after 120 h. The main corrosion product of SS430 was FeS 2 within 48 h and its microstructure was porous. The Cr 6 S 7 was observed again after 72 h. A dense Cr 2 S 3 and FeS 2 coating formed after 120 h, which protected the SS430 and reduced corrosion.

In this study, AISI 430 and HARDOX 450 grade steel are joined using a double-sided tungsten inert gas welding process. The microstructural properties of weld metal and HAZ were evaluated by optical microscopy, energy dispersive spectroscopy, electron back scatter diffraction, elemental mapping, and X-ray diffraction analysis. As the results showed, an increase in welding current caused a large increase in the heat input to the welding pool, the penetration depth and the bead size. AISI 430 steel with Cr and Ni mixed with HARDOX 450 created new phases in the weld metal such as Cr 7 C 3 , Cr 3 Ni 3 , C 23 C 6 , matensite, Cr 1.36 Fe 0.52 . The quantity and compound of martensite and carbides depended on the welding heat output and cooling degree.

In this study, first circular hole layered hybrid composite plates were repaired by wet patch method, and then buckling behavior was investigated experimentally and numerically. In the experimental study, composite plates were produced by vacuum infusion method using hybrid fabrics made of carbon and aramid. Circular holes were drilled in the produced plates and then these holes were repaired with the same material. In the wet patch repair method, wet hybrid fabrics impregnated with epoxy resin were placed around the hole and then this area was subjected to pressure and temperature by vacuum infusion method. In experimental tests, pressure force was applied to the fixed sides and force-displacement graphs were obtained. In a numerical study, non-linear buckling analysis was performed by creating numerical models of plates and patches using the finite element method. As a result, experimental and numerical load-displacement graphs were obtained in accordance with pre- and post-buckling. Thanks to the repair in accordance with practical applications, no interface debonding damage occurred in ideal samples. Increasing the patch length from 30 mm to 40 mm increased the maximum damage load by 6 %, while increasing the patch length to 50 mm increased damage load by 12 %. Increasing the patch thickness from 0.65 mm to 1.1 mm increased the load by 67 %, while increasing it to 2.16 mm increased the load to 247 %. Fiber orientation was found to be a more influencing factor in critical buckling and damage load than the ply sequence.

The response surface method and process capability analysis were conducted in this study to improve evenness, hairiness, imperfections, and tensile strength of ring spun Supima cotton yarn by optimizing values of spinning parameters including traveler mass, yarn density, spindle speed, and yarn twist. The yarns were spun into three densities: 20 Ne, 30 Ne, and 38 Ne. An USTER Tester 5-S800 was used to evaluate the irregularity parameters of yarn. A Lloyd tester was also used to determine the yarn breaking load. The response surface method was applied to optimize the statistical values obtained from the tests of the yarns produced based on the combination values of system parameters. Each response was subjected to a response surface design study, and the optimal values were achieved by using a response optimizer to perform multiple response optimization. Interpreting the response surface design results yielded information such as the absolute values of effects, response degree of significance, data compatibility, and model suitability. Individual desirability, composite desirability, different estimates for each response, and the relationship between response and system variables were all revealed by interpreting the response optimization results. The capability indices of process capability analysis were used to compare process performance before and after response optimization. By interpreting the capability indices’ values of process capability analysis, the capability of the process to meet requirements and improvement potential were acquired. The data was analyzed by implementing Minitab software (Version 19).

The coating is used to provide protection or functional properties to the surfaces of the substrate. In this study, acrylonitrile–butadiene–styrene plastic was coated with copper/ nickel by using an acidic electrolysis deposition method and with aluminum using the physical vapor deposition method. It has been investigated to find out which of these coating methods can be used as an outdoor lighting reflector. Therefore, these two coating methods were compared using sodium carbonate test, scratch test, surface roughness and reflection efficiency tests. In addition, copper/nickel deposited and aluminum deposited on acrylonitrile– butadiene–styrene plastic surfaces were characterized by scanning electron microscopy and energy dispersive X-ray spectrometry. The surface roughness and reflection efficiency of acrylonitrile–butadiene– styrene plastic coated with aluminum applying the plasma vapor deposition method was more efficient than copper/ nickel coated acrylonitrile–butadiene–styrene obtained by applying a non-electric bath method. It has been determined that the samples with electroless copper/nickel coating have a better outdoor resistance than the aluminum coated samples. On the other hand, it was also determined that the surface roughness and reflection efficiency of the aluminum coated samples was better with the plasma vapor deposition method than that of the electroless copper and nickel coated samples. The results show that aluminum coating with the physical vapor deposition method on acrylonitrile–butadiene–styrene plastic is more suitable for reflector technology in terms of light efficiency.

Aluminum alloys and composites are widely used in the field of aviation due to their high strength/weight ratio. However, due to their relatively low hardness values, they have poor wear resistance. In this study, a hybrid composite material was produced through stir casting method. Al 2 O 3 and SiCp particles in 2.5, 5 and 7.5 wt.-% were added into Al2024 matrix material, which is widely used in the aviation industry, in order to increase the wear resistance of composites. The vibratory peening process was applied to the surfaces of the produced samples. The samples were then subjected to a reciprocating wear test. As a result of the tests, it was observed that the vibratory peening process has an important effect on the wear resistance of the samples.

In the current research work, an Al-Si-Mg aluminum alloy-based composite (AMCs) was prepared via stir casting. The AA6082 matrix was incorporated with 0, 3, 6 and 9 wt.-% zirconium diboride (ZrB 2 ) particles for manufacturing composites. The manufactured AA6082/ZrB 2 composites were evaluated by employing scanning electron microscope (SEM) and X-ray diffraction (XRD). Flexural strength, macro-hardness and wear rate of the composites were examined. XRD confirms the development of ZrB 2 peaks and also proves that no reaction products are found in the AMCs. The SEM examination depicts the homogeneous dissemination of ZrB 2 in the Al alloy. The tribological and mechanical characterization of the AMCs improved after the inclusion of ZrB 2 contents. The experimental outcomes attained indicate that the tribological and mechanical behavior of the AMCs was enriched by an escalation in mass proportionate to the ZrB 2 filler content.

Many of today’s rotating shaft systems require the superior stability characteristics of a rotating shaft to prevent system instability. Rotating shaft material properties play a crucial role in the vibration behavior of rotating shaft systems. It is important to control vibrations in the systems because excessive vibration amplitudes can cause inefficiency and system failure. The objective of this study is to investigate the vibration damping capacity of a rotating shaft treated by various procedures (deep cryogenic treatment, induction hardening, hot forging, and conventional heat treatment) in order to see the effects of the treatment procedures. An AISI 4140 steel material for the rotating shaft was selected because it is the most widely used material in industry. The rotating shaft is supported on oil lubricated journal bearings rather than rolling element bearings as used in prior studies by the authors. The results showed that rotating shaft material damping capacity due to treatment processes plays a major role for the rotating shaft systems stability. It is observed that the vibration damping ability of the rotating shaft with induction hardening to dissipate mechanical vibration was superior to deep cryogenic treatment, especially to hot forging and conventional heat treatment processes. Also, the results indicate that the dynamics characteristics of the rotating shafts supported by oil lubricated journal bearings are different to those supported by rolling element bearings.

Fiberglass-reinforced plastic mortar (FRPM) pipes are lightweight, high-strength, and corrosion resistant. Owing to several additional advantages including the ability to convey large flows, convenient installation, and low overall costs, FRPM pipes are well-suited to various pipeline systems in the chemical, water, and drainage industries. As a polymer matrix composite material, the mechanical properties of FRPM pipes are time-dependent. Ring stiffness measures the ability of a pipe to resist deformation under an external load and decreases with increasing service time. Reduced ring stiffness can lead to excessive deformation, which can affect the long-term durability of the pipeline, eventually resulting in failure. At present, only few studies have been conducted on long-term ring stiffness of FRPM pipelines, which has hindered their application. In this study, long-term ring stiffness of 500 mm diameter pipes comprised of FRPM was tested under two different loading conditions: constant load and constant displacement. Variation of ring stiffness with time under constant load and constant displacement conditions was obtained and the predicted attenuation of ring stiffness after 50 years was found to be 11.62 % and 15.48 %, respectively, which further confirms the reliability of long-term ring stiffness predictions based on short-term test data. And the results will contribute to further studies on the longterm ring stiffness of FRPM pipes.