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This study investigates the mechanical, fatigue, and microstructural properties of friction stir welded dissimilar AA6061-AZ31B Mg alloy, incorporating cassava waste biosilica. The principal aim of this research study was to analyze the reinforcement effect of biosilica in the weld pool of dissimilar AA6061-AZ31B Mg subjected to friction stir welding process. The biosilica of size 30–40nm was synthesized from the waste of cassava peel via thermo-chemical process and characterized. The welding process was performed as a butt joint configuration with the biosilica filled via the root canal. According to the results, the weld bead AA2 demonstrates notable tensile and yield strength of 252 and 218MPa, respectively, with a notable elongation of 4.4%. Despite this, it shows a maximum impact energy of 17.8J, signifying favorable toughness. Biosilica inclusion enhances hardness, peaking at 112 VHN for weld composition AA3, crucial for wear resistance. Composition AA2 exhibits noteworthy fatigue strength at 158MPa, vital for industries like automobile and defense. The microstructure of welds revealed changes in grain size and toughness improvement after the addition of biosilica. The EDAX report confirms the presence of Si, Al, and Mg atoms in the nugget zone. The weld composition AA2 showcases promising mechanical properties, suggesting its suitability for demanding applications in these sectors. In summary, biosilica incorporation in friction stir welding enhances mechanical properties, providing useful strength improvement for commercial and novel MMCs developed for robust applications.

Rotating bending fatigue tests were carried out in order to investigate effects of shot peening and laser peening treatment on fatigue properties of degassing processed cast aluminum alloys. Degassing was useful for decreasing cast defects and increasing the range of fatigue life and fatigue strength at 10⁷ cycles compared with those of non-degassed cast alloys. The shot peening and the laser peening treatments also showed remarkable effects for increasing the resistance of crack propagation behaviors and improving the fatigue strength of the degassing processed cast aluminum alloys.

The initial crack under fretting condition occurs at lower stress amplitude and lower cycles of cyclic loading than that under plain fatigue condition. The fretting damage, for example, can be observed in fossil and nuclear power plant, aircraft, automobile and petroleum chemical plants etc. INCONEL alloy 690 is a high-chromium nickel alloy having excellent resistance to many corrosive aqueous media and high-temperature atmospheres. This alloy is used extensively in the industries of nuclear power, chemicals, heat-treatment and electronics. In this paper, the effect of fretting damage on fatigue behavior for INCONEL alloy 690 was studied. Also, various kinds of tests on mechanical properties such as hardness, tension and plain fatigue tests are performed. Fretting fatigue tests were carried out with flat-flat contact configuration using a bridge type contact pad and plate type specimen. Through these experiments, it is found that the fretting fatigue strength decreased about 43% compared to the plain fatigue strength. In fretting fatigue, the wear debris is observed on the contact surface, and the oblique micro-cracks are initiated at an earlier stage. These results can be used as the basic data in a structural integrity evaluation of heat and corrosion resistant alloy considering fretting damages.

Mechanical performance parameters such as the fatigue strength, tensile strength, ductility and Young's modulus of newly developed Ti-29Nb-13Ta-4.6Zr, referred to as TNTZ, can be improved considerably by microstructural control via thermomechanical processing. Thermomechanical processing including severe cold wire drawing can generate functionalities such as super elasticity in TNTZ. The abovementioned improvement in the mechanical performance and functionality of TNTZ is associated with its nanosize structure. The cytotoxicity of TNTZ is very low and equivalent to that of pure titanium. It is expected that TNTZ will be used as a structural biomaterial.

Aluminium has good corrosion properties and a high strength to weight reduction which makes it favourable in many applications. The increased use of aluminium casting in the automotive industry does also imply that the need for design data for aluminium increases. Especially for castings, the influences of casting defects are always an issue. For this reason fatigue properties for as-cast sand and permanent mould specimens with different contents of porosity have been studied. The cast aluminium specimens of two different porosities were fatigue tested in cyclic axial test at R=-1. Prior to fatigue test specimens were examined by CT-scan and sorted into two quality groups depending on the porosity level.

The aim of this work was to investigate the fatigue life for cast AC4C-T6 alloy with different amounts of inherent porosity. An additional aim was to predict the durability for cast components with defect constrained in a specified volume of components, by using a commercial program MSC. Fatigue.

Incoloy 800, which is used within steam generator tubes, is a heat resistant material since it is an iron-nickel-chromium alloy. However, construction of a systematic database is needed to receive integrity data defecting insurance of specific data about room and elevated temperature fretting fatigue behavior for Incoloy 800. Accordingly, this study investigates the specific change in fatigue limitations under the condition of the fretting fatigue as compared to that under the condition of the plain fatigue by performing plain and fretting fatigue tests on Incoloy 800 at 320°C, real operating temperature and at room-temperature, respectively. The change in the frictional force is measured during the fretting fatigue testing against the repeated cycle, and the mechanism of fretting fatigue is investigated through the observation of the fatigue-fracture surface.

7003-T5 Aluminum (Al) alloy plates with a thickness of 5 mm are welded by gas metal arc welding (GMAW) method in this work. In order to investigate the influence of stress concentration introduced by weld reinforcement on fatigue strength, the stress concentration factor of the butt joint is calculated. Microscopic and X-ray techniques were utilized to make sure there are no weld defects with large size in butt weld, which can induce extra stress concentration. The cyclic stress – number of cycles to failure (S–N) curves of the joints with and without the welder were obtained by fatigue testing, and the results show that the fatigue strength of 7003-T5 Al alloy butt joints with the weld reinforcement is 50 MPa, which is only 45% of the joints without the weld reinforcement. Fracture surface observation indicated that the fatigue source and propagation are dissimilar for the specimens with and without the welder due to the stress concentration at the weld root. The stress concentration with a factor of 1.7 has great effect on the fatigue strength, but little influence on the tensile strength.

Two dissimilar Al alloys, 5083-H111 and 6005A-T6, were joined by hybrid laser–MIG welding method. Mechanical properties of the welded joint were investigated and compared. The results show that the tensile strength of the dissimilar joint is 219.8 MPa, 11.7% higher than that of 6005A-T5 joint. After statistical analysis of the fatigue data, the $P$–$S$–$N$ curves of the dissimilar joint were obtained. The mean fatigue strength at $N_f=10^7$ of the dissimilar joint is 112.5 MPa. The fatigue strength at $N_f=10^7$ of the dissimilar joint for a given 10% probability of failure, at a confidence level of 95%, is 101.4 MPa. The fatigue strength at $N_f=10^7$ of the dissimilar joint is almost same as that of the 6005A-T6 joint. In welded structure designing, different $P$–$S$–$N$ curves should be chosen according to the different service conditions and reliability requirements.

Stress concentration is a key factor that affects the fatigue strength of welded joints. In this study, the fatigue strengths of butt joints with and without the weld reinforcement were tested to quantify the effect of stress concentration. The fatigue strength of the welded joints was measured with a high-frequency fatigue machine. The $P$–$S$–$N$ curves were drawn under different confidence levels and failure probabilities. The results show that butt joints with the weld reinforcement have much lower fatigue strength than joints without the weld reinforcement. Therefore, stress concentration introduced by the weld reinforcement should be controlled.

In this study, dissimilar material welding between Alloy617 and 12Cr steel was performed using buttering welding technology on to the 12Cr steel side. Then, the welding residual stress of dissimilar material weld was analyzed by the numerical method and the experimental method, after that, the stress amplitude including the welding residual stress was calculated using a modified Goodman equation.

To improve the fatigue strength of the roller chain, the fatigue test is conducted by varying the press-fitting ratio between the pin and the holed plate. To model what occurs in a chain under load, a single plate specimen is prepared by press-fitting two pins into two holes at the ends of the plate. The FEM analysis is performed to obtain the stress amplitude and the average stress. The results, in both cases demonstrate that the fatigue strength is improved by the press-fit between the pin and the hole. The fatigue improvement mechanism is discussed based on the stress analysis.

A prosthetic knee is predominantly subjected to cyclic action leading to fatigue failure during its operation. However, cyclic failure is more severe as it occurs below the yield strength and may happen even without prior indication. This study presents a cyclic structural analysis of an existing polycentric mechanical prosthetic knee by finite element simulation and its experimental validation as per the ISO 10328:2016 standard. The three-dimensional (3D) model is imported to the ANSYS 20.1 workbench to study stress distribution and fatigue life in the knee for ensuring its safety performance. The maximum von-Mises stresses developed at the front and back joint bars made of A390.0-T5 and A390.0-T6 cast aluminium are 100 and 89MPa, respectively, in both loading conditions compared to their mechanical fatigue strength of 89MPa. The maximum deformation and average number of cycles for fatigue failure are 2.66 and 2.53mm and $2.95\times 10^6$ and $2.81\times 10^6$ for simulation and experimental results, respectively. These results suggest that this polycentric knee unit has poor fatigue strength and thereby does not meet the ISO structural standard. A validation test has been performed with an average error of 4.75% between the simulation and experiments results showing higher reliability.

In order to study the influence of different stenosis rates of blood vessels on the fatigue strength and service life of lower limb arterial stent, numerical simulation was conducted for the mechanical behavior of four types of nickel-titanium alloy lower limb arterial stents (Absolute Pro, Complete SE, E-luminexx-B and Pulsar-35) under the action of radial compression, release and pulsating loads, so as to predict the fatigue life and safety of stents at different stenosis rates (0%, 30%, 50% and 70%). The study found that with increased vascular stenosis rate, both the elastic stress and strain of stent tend to increase, while the fatigue strength, service life and safety tend to decrease. When a stent is implanted in a normal blood vessel, its fatigue strength satisfies the requirement of a 10-year service life requirement, with maximum elastic stress and strain occurring on both sides of the connecting ribs at the end of stent. When the vascular stenosis rate is greater than 30%, the fatigue strength of the stent does not meet requirement of a 10-year service life, and fatigue fracture is likely to occur at the most stenotic part of the blood vessel. With increased vascular stenosis rate, the E-luminexx-B stent with the largest width of support had a significant decrease in its service life. The stent whose supporting unit is of symmetric wave peak structure has a longer service life compared with that whose supporting unit is of offset wave peak structure. The revealing of the influence of vascular stenosis rate on the mechanical properties and fatigue life of stents provides theoretical reference for the fracture failure mechanism of stents.

Polymethylmethacrylate (PMMA) is the most widely used material for denture base constructions. However, its resistance to impact, bending and fatigue is somewhat poor. Therefore, fracture of acrylic resin denture bases is still a frequently encountered problem in prosthodontics. The impact strength, transverse strength and fatigue resistance of heat polymerised acrylic resin reinforced with chopped strand mat (CSM), surface tissue (ST) and unidirectional laminate (UL) from E-Glass of various volume (2.5, 3.0, 4.0, 5.0%) were investigated and assessed. The fractured surface photographs were taken by SEM. The results revealed that in comparison with the unreinforced specimens were significantly increased.

The super-high strength sucker rod is widely used in Chinese oil companies. The fatigue limit is one of most important features of super-high sucker rod. The fatigue strength experiment and reliability analysis were carried out according to petroleum industry standard. The alternating stress loading cycles before sucker rod fatigue failure were obtained under three different load levels, and then the experiment data were counted by probability statistic. The P-S-N formula and fatigue limit were calculated based on the experiment data, which applies theoretical basic to sucker rod design for oil lifting.

High cycle fatigue (HCF) property of one kind of near alpha titanium alloy named after Ti-600 was investigated at a frequency of 120~130Hz and with a load ratio R of 0.1. The HCF strength for the alloy at ambient temperature was found to be 475MPa. The observed high HCF strength was attributed to its overlapping plate like α+β phase microstructure. At the same stress of 600MPa, the distance between two fatigue stripes for the sample fractured at 8.61×10⁵ cycles was wider than that of the sample failured at 1.78×10⁶ cycles, which indicated that their propagation resistance for fatigue cracks was smaller.