Fatigue Life Optimization Research Articles

Optimization of fatigue life of the seismic vibrator baseplate considering the coupling effect of welding residual stress

The seismic vibrator baseplate (SVB) is a welded structure. Ignoring welding residual stress (WRS) and only considering cyclic stress can decrease the accuracy of fatigue life assessments. This study aims to investigate the fatigue life prediction and optimization of SVB under the influence of WRS. A welding model of SVB and an SVB-ground excitation model were developed, and the stress distribution of SVB was determined using the finite element method. A fatigue life prediction study that incorporates WRS, based on a modified S-N curve, was conducted. A multi-objective fatigue life optimization analysis was performed using genetic algorithms. The results shows that the backing weld (BW) of the SVB is the most susceptible area to fatigue failure. Under the combined effects of WRS and working stress, the fatigue life of the SVB is 8.14 years. When considering WRS, the prediction results align well with field data, showing an error margin of less than 5 %. WRS is identified as a critical factor influencing the fatigue life of SVB, and optimizing welding parameters can effectively reduce WRS, thus extending the service life. The optimal welding parameters were found to be welding interpass temperature of 105 °C and welding speed of 10.23 mm/s. After optimization, the fatigue life of the SVB increased to 10.23 years, a 25.68 % improvement over the pre-optimization condition. Previous studies did not consider the influence of WRS, whereas this work integrates it into the fatigue analysis, producing a modified S-N curve that enhances the accuracy of life prediction. Furthermore, multi-objective optimization algorithms and fusion decision-making methods were applied to the fatigue life optimization of the SVB, offering novel research approaches and methodologies. This study provides theoretical guidance for the structural design and optimization of the SVB, aligning with practical engineering needs and showing substantial application value.

Heat build-up and thermo-mechanical fatigue life optimization of aircraft tire using deformation index concept

Heat build-up and thermo-mechanical fatigue life optimization of aircraft tire using deformation index concept

Fatigue life optimization and lightweight design of wheel based on entropy weight grey relation analysis and modified NSGA-II

In order to study the fatigue performance of wheel and enhance its lightweight design level, this article proposes the structure, design and optimization method of magnesium-aluminum alloy assembled wheel. Taking a [Formula: see text] type wheel as the research object, the optimal topology of wheel spoke is solved by constructing a topology optimization model for wheel bending and radial fatigue test conditions. A finite element model for bending and radial fatigue testing of assembled wheels was established, which simulates and analyzes the fatigue performance and its influencing factors of the wheel under two working conditions. Combined with contribution analysis method, the modified NSGA-II and entropy weight grey relation analysis (EGRA), the multi-objective optimization of assembled wheel was performed. The result demonstrated that the weight reduction of the assembled wheel after optimized design is 4.49%, while the bending fatigue life and radial fatigue safety factor are decreased by 9.95% and 25%, respectively. In order to better balance the performance of assembled wheel and achieve lightweight design, this article combines the joint topology optimization of assembled wheels with multi-objective optimization method for multiple working conditions and screens the optimal compromise solution by EGRA, which provides an approach for wheel lightweight design and multi-objective optimization.

Mechanical properties of Sn–Pb based solder joints and fatigue life prediction of PBGA package structure

Solder joints are generally the weakest part in electronic packaging structure whose fatigue life depends to a large extent on the durability of solder joints. In pursuit of a balance between environmental protection and soldering performance, commonly used Sn–Pb solder should be modified by adding other chemical elements to reduce Pb content. This work aims to investigate the performance of different solder materials and explore the impact of different electronic package structures. Firstly, tensile experiments are performed on three kinds of solders (Sn–Pb, Sn–Pb–In, Sn–Pb–Bi) to obtain their mechanical behavior, and then the constitutive laws of them are calibrated by Anand model. Additionally, finite element method (FEM) is used simulate the response of plastic ball grid array (PBGA) package structure under thermal cycles, and mechanical variables including deformation, equivalent stress, and equivalent strain are analyzed. Finally, Coffin-Manson and Engelmaier equations are adopted to predict the fatigue life of package structures and the effects of various factors such as solder materials, dimensions of components, and welding quality are further investigated. Results reveal that adding Bi into Sn–Pb solder can make the solder joints have better performance. From the perspective of optimum fatigue life, the plastic package thickness is recommended in the range of 0.8 mm–0.9 mm, the chip thickness is recommended as 0.35 mm, the substrate thickness is recommended to be less than 0.34 mm, and the ratio of stand-off height to solder ball diameter should be controlled between 0.6 and 0.7. According to the prediction, the solder ball diameter is suggested to be 0.54 mm so that fatigue life could reach 194 cycles, and the stand-off height for this package structure is suggested to be 0.36 mm so that fatigue life could reach 123 cycles.

Design and optimization of squirrel cage geometries in aircraft engines toward robust whole engine dynamics

In this work, an coupled end-to-end approach for the optimization of the rotor dynamic behavior of a dual-spool aircraft engine along with fatigue life optimization of squirrel cages (SQC) is presented. A realistic model to simulate the rotor dynamics is created, where the high-pressure (HP) rotor is supported by two squirrel cages. The aim of this work is to find a robust rotor dynamics design by shifting a critical speed to higher rotational speed, and at the same time improving the squirrel cage design with respect to fatigue life. Fully automatized coupled analysis process chain is implemented, allowing to compute the influence of the SQCs geometry variation onto the full rotor dynamics and structural performance of the SQC. Two global optimization techniques are employed to explore the SQCs design space and find optimal 3D geometries, using the aforementioned coupled process. Optimization results are compared and discussed in detail, indicating the importance of the numerical optimization to improve fatigue life of the squirrel cage. It is shown that optimized and non-optimized SQC designs, both fulfilling rotor dynamics goals, can have significantly different performance regarding their fatigue life. Moreover, the advantage of the coupled process is illustrated, allowing to find superior SQC designs by considering both disciplines simultaneously in comparison with a sequential (uncoupled) approach, when the target elastic properties of an SQC, selected only based on the rotor dynamics requirements, may lead to sub-optimal fatigue life.

Data-driven bending fatigue life forecasting and optimization via grinding Top-Rem tool parameters for spiral bevel gears

To establish a bridge between grinding tool parameters and loaded tooth fatigue life, an innovative data-driven root flank bending fatigue life forecasting and optimization via Top-Rem tool parameters was proposed for grinding spiral bevel gears. The recent machine settings modification is extended into grinding Top-Rem tool parameters modification in case that geometric accuracy and root bending fatigue life are integrated into a collaborative optimization. The proposed Top-Rem modification includes three key steps: (I) arc-shaped blade, (II) top part, and (III) top fillet part. Then, while root bending stress is determined by using finite element method (FEM)-based simulated loaded tooth contact analysis (SLTCA), data-driven fatigue life forecasting is developed by correlating with the multiaxial fatigue damage model based assessment. Moreover, data-driven bending fatigue life optimization model is established by using Top-Rem tool parameters modification, where the important constraints in target flank determination includes: (i) root overcutting, (ii) geometric accuracy, and, (iii) fatigue life. For high accuracy and efficiency, two different strategies are proposed: (i) the different parameters modification types; and, (ii) sensitivity analysis of grinding Top-Rem tool parameters. Finally, proposed method can verify that bending fatigue life can be significantly improved by modifying the key Top-Rem tool parameters in early stage of the whole life product development for spiral bevel gears.

Optimization of fatigue life of pearlitic Grade 900A steel based on the combination of genetic algorithm and artificial neural network

In this paper, the fatigue life of pearlitic Grade 900A steel used in railway applications is investigated. To predict the fatigue life of pearlitic Grade 900A steel based on the number of cycles of the particular stress level in the load block, occurrence ratio and overload ratio, a feed-forward neural network is designed. The results of this artificial neural network are compared to the surface fitting method. Then sensitivity analysis is applied to the obtained artificial neural network values to measure the effect of each input parameter on the fatigue life. Finally, the genetic algorithm is applied to find the maximum fatigue life based on the input values.

Fatigue life optimization for 17-4Ph steel produced by selective laser melting

PurposeThe mechanical characterization of selective laser melting (SLM) parts is an industrial challenge. This paper aims to propose a methodology to control the fatigue life of 17-4Ph stainless steel by selecting the most relevant manufacturing parameters: i.e. laser power, laser travel speed, hatch spacing and laser defocusing.Design/methodology/approachA rough and refined design of experiment (DOE) is carried out to target the best combination of process parameters. A response surface model is then constructed to predict the parameter combination that optimizes the fatigue performance.FindingsThis study results show that the fatigue limit of the specimens manufactured by SLM (471.7 MPa at 107 cycles) has reached near 90% of the value found in samples machined from a bar. This demonstrates the applicability of the method proposed to optimize the SLM process and control the fatigue life of 17-4Ph stainless steel. The study results are compared with other research works and provide an increase of 18% to the fatigue limit.Originality/valueThis study showcases a DOE methodology to optimize the SLM parameters to achieve fatigue performance as great as that of solid 17-4Ph stainless steel.

Effects of Pre-Tensile Deformation on the Fatigue Fracture Behavior of Annealed 7005 Aluminum Alloy Plate.

In the present study, the fatigue life and fatigue fracture characteristics of annealed 7005 aluminum alloy plates subjected to different pre-tensile deformations were investigated. The results obtained upon increasing the pre-tensile deformation of the alloy plate to 20% revealed that the second-phase particles did not show any obvious changes, and that the thickness of the thin strip grain slightly decreased. The dislocation distribution in the alloy matrix varied significantly among the grains or within each grain as the dislocation density gradually increased with increasing pre-tensile deformation. Moreover, the fatigue performance of the annealed 7005 aluminum alloy plate was significantly improved by the pre-tensile deformation, and the alloy plate subjected to 20% pre-tensile deformation exhibited an optimal fatigue life of ~1.06 × 106 cycles, which was 5.7 times and 5.3 times that of the undeformed and 3% pre-stretched alloy plates, respectively. Two fatigue life plateaus were observed in the pre-tensile deformation ranges of 3–5% and 8–12%, which corresponded to heterogeneous dislocation distribution among various grains and within each grain, respectively. Moreover, two large leaps in the plot of the fatigue-life–pre-tensile-deformation curve were observed, corresponding to the pre-tensile deformation ranges of 5–8% and 16–20%, respectively.

Optimization of fatigue life in laminated composite plates

Abstract With the development of fiber technology on which the composite materials depend mainly was necessary to improve the rigidity, durability, and heat transfer in the areas of heating and cooling technologies. The effect of the fatigue phenomenon on composite materials using carbon fibers is studied. In this research paper, work was performed to study the improvement in the bearing capacity of the stress test sample with the addition of carbon fibers at different angles. The stresses affecting the test specimen are cylindrical with a length of 10 cm. The results proved that the best arrangement of the carbon fibers in the form of triple layers starting from the center of the cylinder circle to the outside was the share of the arrangement layer 45, 0, 0, where the lowest value was the number of fatigue life cycles, 2349 cycles in the bending test, as the amount of stress that this case reached was 6.1×108 Pa compared to the rest of the studied cases.

Prediction and optimization of fatigue life of an axial bladed disk with intentional mistuning

Prediction and optimization of fatigue life of an axial bladed disk with intentional mistuning

Experimental Optimization for Fatigue Life Maximization of Additively Manufactured Ti-6Al-4V Alloy Employing Ultrasonic Impact Treatment

Ultrasonic Impact Treatment (UIT) is an effective surface modification method used to increase fatigue life of welding application by inducing compressive residual stresses. In this paper, we extend the application of UIT to include additively manufactured metallic parts with particular focus on Ti-6Al-4V manufactured with Direct Metal Laser Sintering technology. Design optimization for the application parameters of the UIT was conducted with the objective of fatigue life maximization. Application parameters of the UIT included the static pre-stressing force of UIT impact needle against the treatment surface and its scanning speed during application while the scanning pattern is maintained constant. Results show that a static load of 30N and a scanning speed of 2000mm/min can provide an optimal fatigue life increase up to 250% compared to untreated parts. It is shown that the increase in fatigue performance correlates strongly with an increase in the micro-hardness and compressive residual stress and less strongly with surface roughness. Two Stress-Life (S-N) curves are fully characterized experimentally based on a set of samples treated with the determined optimal UIT parameters and another set of untreated versions. Endurance limit of the optimally treated specimens is increased by 25% from about 200-250MPa.

Processing, structure, and properties of additively manufactured titanium scaffolds with gyroid-sheet architecture

While the relationships between processing, structure, and properties of solid titanium alloys produced by additive manufacturing have been established, these relationships are less understood for porous materials, particularly those with rough surfaces inherent to L -PBF. For orthopedics applications, porous architecture and surface roughness are desirable for bone growth, and thus optimization of fatigue life despite these inherent fatigue drivers is critical. The present results establishes relationships between post-processing, microstructure, and resulting fatigue properties for gyroid-sheet scaffolds with as-fabricated surfaces. By comparison of known factors driving fatigue behavior, the relative effect of each on normalized fatigue strength was quantified. Normalized compressive fatigue strength of the gyroid-sheet scaffolds which underwent no surface treatments was observed to be > 50%. The result is higher than that seen for tension fatigue of analogous gyroid-sheet scaffolds, or compared to previously reported normalized compressive fatigue strength of strut based scaffolds. The high strength and fatigue resistant behavior of gyroid-sheet scaffolds despite the inherent surface roughness of L -PBF is desirable for biomedical applications.

Optimization of fatigue life and fractography analysis of knuckle joint

Steering knuckle is an important component of a vehicle suspension system, which acts as a connection point between the wheel hub and the suspension system. Since, the forces coming from the tires are transferred to knuckle with high varying loads. The design of a knuckle becomes very critical in terms of its life with high factor of safety. At the same time, the design also should be robust with the required fatigue life, right material selection and weight optimization, without affecting the desired performance. There has been a considerable effort placed in this direction to reduce the overall weight of the knuckle system by employing high strength alloys instead of conventional materials or optimizing the geometry without altering the desired functionality and its fatigue life. This project focuses on optimization and fatigue life estimation of an optimized Knuckle using Finite Element Analysis approach and fatigue tester. This is done by studying and comparing the results of a rigid baseline model with that of an optimized model through simulation and experimentation. The optimized model is arrived based on the stresses obtained from the baseline study. The fatigue life of the optimized model is evaluated under fatigue tester and fractography analysis is carried out.

Fatigue life optimization towards rubber core sealing surface of under-balanced drilling rotating blowout preventer

In the process of under-balanced drilling, the rubber core of rotating blowout preventer (RBOP) subject to the alternating cycle load was prone to fatigue failure. Firstly, the sealing principle of RBOP was analyzed and the stress of rubber core in dynamic sealing process was obtained. Then, the Yeoh constitutive model in the deformation process was established by the tensile test of the rubber core material. Then we used ABAQUS software to establish the finite element model of the dynamic sealing of the rubber core, and the simulation of the sealing process of the rubber core during the drilling and tripping operations and the optimization analysis of the factors affecting the fatigue life of the sealing surface of the rubber core were carried out. In this paper, the structure of the rubber core was optimized, and the optimal outer angle of the rubber core was 155°, the inner angle was 153°, and the base angle was 125°. Then the inner diameter size of rubber core that was matched with different outer diameter drill pipes was optimized and the best combination of rubber core was obtained. The paper also optimized the lowering and lifting speed of drill pipe under different wellhead pressures. The higher the well pressure, the more likely the rubber core fatigue failure would be. The safe lowering and lifting speed of drill pipe under different pressures was obtained. At last, according to the Chinese standard, indoor seal test and field application test were carried out in the Well Control Equipment Quality Supervision and Inspection Center of China national petroleum industry to confirm the reliability of finite element optimization, which was of great practical significance to improve the service life of rubber core and oilfield operation safety.

Property optimization of low-cycle fatigue in Al-Si piston alloy at elevated temperatures by ultrasonic melt treatment

The cyclic deformation and damage behaviors of Al-Si piston alloys are comprehensively studied. It is found that the fatigue cracks mainly initiate from broken primary Si at low temperature and phase/matrix interface debonding at higher temperature. The transgranular crack propagation can be found for all the temperatures and the grain is obviously reduced after low-cycle fatigue at higher temperature. Furthermore, a hysteresis energy-based life prediction model was developed and utilized. Based on the model, the optimum fatigue life was found at intermediate temperature. A strategy for fatigue property optimization was proposed: increasing W0 at low temperature and increasing β at high temperature, to enhance the fatigue life during entire service temperatures with the ultrasonic melt treatment. In this way, the remarkable improvement of the fatigue properties may be achieved.

Effect of optimal shot peening time on fatigue life for aluminum alloy 6061-T651

The compressive residual stresses generated by shot peening, is increased in a direct proportional way with shot peening time (SPT). For each metal, there is an optimum shot peening time (O.S.T) which gives the optimum fatigue life. This paper experimentally studied to optimize shot peening time of aluminium alloy 6061-T651 as well as using of and analysis of variance (ANOVA).
 Two types of fatigue test specimens’ configuration were used, one without notch (smooth) and the other with a notch radius (1,25mm), each type was shot peened at different time. The (O.S.T) was experimentally estimated to be 8 minutes reaching the surface stresses at maximum peak of -184.94 MPa.
 A response surface methodology (RSM) is presented to optimize the surface properties of fatigue life due to effect of two parameters (shot peening time and fatigue stresses). A statistical software was used to perform analysis of variance (ANOVA) to predict the optimum shot peening time. The results were 8.007 minutes without notch and 7.53 minutes with notch. Two 2nd degree polynomials were obtained for the two studied cases with confidence level of 95%. Experimentally26.67% enhancement in fatigue life was obtained, but after using (RSM), the results gave 61% improvement, compared with ref. [2].

Design Optimization of Rolling Element Bearings Using Advanced Optimization Technique

This article concentrates on optimization of fatigue life, i.e., dynamic capacity of rolling element bearings by using a novel optimization approach known as Teaching–Learning-Based optimization. The optimization technique is applied to two cases of bearing, i.e., deep groove ball bearing and cylindrical roller bearing, by considering a large number of bearings and their associated constraints. The chosen problems involve around 9 design variables and the optimized result obtained shows considerable improvement over the previous results, standard catalogues and handbooks. Efforts are also made to validate the obtained results using finite element analysis approach and the simulated results of contact stress and deformation at the contact between inner race and roller are found in close agreement with the obtained optimum results. Thus, this article proves good applicability of proposed optimization approach in bearing design which will be useful to the on field designers to improve the performance of bearings.

Composite laminate design with strength and fatigue life optimization using Elite–Scout Genetic Algorithm (ESGA)

Genetic algorithm (GA)-based optimization is a common approach to deal with problems that have a large solution space. Composite laminate design is one such problem due to the substantial number of candidates that arise from the selection and stacking of lamina. Many authors have successfully demonstrated GA-based approach in stacking sequence optimization. A few of them extending it to as far as selecting the candidate lamina for the candidate laminate. However, a vast majority of the literature is limited to optimizing a single parameter such as Margin of Safety, Buckling Load Factor, etc., while neglecting other parameters or assigning ill-suited weights to obtain a unified fitness function. In this paper, we will be discussing a novel Elite–Scout Genetic Algorithm (ESGA) for multi-objective optimization which will result in the Pareto-optimal solution(s). The algorithm is based on the first multiple elitist selection method, integrated with the concept of a scout operator. ESGA incorporates a population dependent growing crossover rate, and decaying mutation rate. The growth and decay are modeled along the lines of the cooling schedule as found in simulated annealing (SA). This will ensure greater flexibility of the algorithm by accommodating better exploration of the solution space without deterring the convergence of the solution.

The Effect of Controlled Shot Peening on the Microstructure and Fatigue Behavior of Wet Copper-Based Powder Metallurgy Friction Plates

The effects of shot peening treatments on the microstructure and fatigue behavior of the teeth root in wet copper-based powder metallurgy friction plates were investigated and an efficient method for selecting optimal shot peening parameters for friction plates was proposed. Different experimental processes including microscopy observation, microhardness, roughness and X-ray diffraction measurements have been performed to characterize the treated surface of specimens. It is found that fatigue life of friction plates firstly increases and then decreases with the increase of Almen intensity, and the optimal fatigue life has improved over 55%. It is considered that both surface grain refinement and high residual compressive stress are the main ingredients responsible for the improved fatigue life. With further increase of Almen intensity, surface roughness of the teeth root gradually increases to a critical point, where rough peened surface may induce crack initiation due to stress concentration, and finally lead fatigue deteriorate.