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Article
Publication date: 11 August 2023

Jianhui Liu, Ziyang Zhang, Longxiang Zhu, Jie Wang and Yingbao He

Due to the limitation of experimental conditions and budget, fatigue data of mechanical components are often scarce in practical engineering, which leads to low reliability of…

Abstract

Purpose

Due to the limitation of experimental conditions and budget, fatigue data of mechanical components are often scarce in practical engineering, which leads to low reliability of fatigue data and reduces the accuracy of fatigue life prediction. Therefore, this study aims to expand the available fatigue data and verify its reliability, enabling the achievement of life prediction analysis at different stress levels.

Design/methodology/approach

First, the principle of fatigue life probability percentiles consistency and the perturbation optimization technique is used to realize the equivalent conversion of small samples fatigue life test data at different stress levels. Meanwhile, checking failure model by fitting the goodness of fit test and proposing a Monte Carlo method based on the data distribution characteristics and a numerical simulation strategy of directional sampling is used to extend equivalent data. Furthermore, the relationship between effective stress and characteristic life is analyzed using a combination of the Weibull distribution and the Stromeyer equation. An iterative sequence is established to obtain predicted life.

Findings

The TC4–DT titanium alloy is selected to assess the accuracy and reliability of the proposed method and the results show that predicted life obtained with the proposed method is within the double dispersion band, indicating high accuracy.

Originality/value

The purpose of this study is to provide a reference for the expansion of small sample fatigue test data, verification of data reliability and prediction of fatigue life data. In addition, the proposed method provides a theoretical basis for engineering applications.

Details

International Journal of Structural Integrity, vol. 14 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 17 October 2023

Yaobing Wei, Yanan Li, Jianhui Liu, Gai Wang, Yanlei Guo and Xuemei Pan

In practical engineering, oil filters often work under asymmetric cyclic loading. In order to improve the prediction accuracy of fatigue life of the oil filters under asymmetric…

Abstract

Purpose

In practical engineering, oil filters often work under asymmetric cyclic loading. In order to improve the prediction accuracy of fatigue life of the oil filters under asymmetric cyclic loading, the effect of strain ratio and low cycle fatigue plastic deformation on fatigue life need to be considered. This paper aims to discuss the aforementioned objective.

Design/methodology/approach

First, strain-controlled fatigue tests with strain ratios of 0, 0.5 and −1 were carried out on the oil filter material 2A70-T6 aluminum alloy, and the test data were used to obtain strain fatigue life curves at three strain ratios. Then, based on the idea of the constant life curve method, the average value of the ratio of the strain amplitude corresponding to different strain ratios under the same partial life was defined as the strain ratio factor. Finally, the elastic-plastic factor was modified by the strain ratio factor, and a new fatigue life prediction model considering the effect of strain ratio was proposed.

Findings

The proposed model was validated, respectively, by fatigue test data of 2A70-T6 aluminum alloy, 2124-T851 aluminum alloy and oil filter and the results of the proposed model were compared with the Coffin–Manson equation, Morrow model and Smith–Watson–Topper (SWT) model, showing that the proposed model had higher applicability and accuracy.

Originality/value

In this work, a strain ratio factor is established based on the idea of the constant life curve method, and the strain ratio factor is used to modify the introduced elastic-plastic factor, and then a new fatigue life prediction model considering the influence of strain ratio and low cycle fatigue plastic deformation on material fatigue damage accumulation is proposed. The results show that the prediction results of the proposed model are in good agreement with the experimental data, and the proposed model has good fatigue life prediction ability considering the influence of strain ratio and lays a foundation for the fatigue life prediction of the oil filter.

Details

International Journal of Structural Integrity, vol. 14 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 8 September 2023

Xintian Liu and Muzhou Ma

Scholars mainly propose and establish theoretical models of cumulative fatigue damage for their research fields. This review aims to select the applicable model from many fatigue…

Abstract

Purpose

Scholars mainly propose and establish theoretical models of cumulative fatigue damage for their research fields. This review aims to select the applicable model from many fatigue damage models according to the actual situation. However, relatively few models can be generally accepted and widely used.

Design/methodology/approach

This review introduces the development of cumulative damage theory. Then, several typical models are selected from linear and nonlinear cumulative damage models to perform data analyses and obtain the fatigue life for the metal.

Findings

Considering the energy law and strength degradation, the nonlinear fatigue cumulative damage model can better reflect the fatigue damage under constant and multi-stage variable amplitude loading. In the following research, the complex uncertainty of the model in the fatigue damage process can be considered, as well as the combination of advanced machine learning techniques to reduce the prediction error.

Originality/value

This review compares the advantages and disadvantages of various mainstream cumulative damage research methods. It provides a reference for further research into the theories of cumulative fatigue damage.

Details

International Journal of Structural Integrity, vol. 14 no. 5
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 12 January 2023

Shaoyi Liu, Songjie Yao, Song Xue, Benben Wang, Hui Jin, Chenghui Pan, Yinwei Zhang, Yijiang Zhou, Rui Zeng, Lihao Ping, Zhixian Min, Daxing Zhang and Congsi Wang

Surface mount technology (SMT) is widely used and plays an important role in electronic equipment. The purpose of this paper is to reveal the effects of interface cracks on the…

Abstract

Purpose

Surface mount technology (SMT) is widely used and plays an important role in electronic equipment. The purpose of this paper is to reveal the effects of interface cracks on the fatigue life of SMT solder joint under service load and to provide some valuable reference information for improving service reliability of SMT packages.

Design/methodology/approach

A 3D geometric model of SMT package is established. The mechanical properties of SMT solder joint under thermal cycling load and random vibration load were solved by 3D finite element analysis. The fatigue life of SMT solder joint under different loads can be calculated by using the modified Coffin–Manson model and high-cycle fatigue model.

Findings

The results revealed that cracks at different locations and propagation directions have different effect on the fatigue life of the SMT solder joint. From the location of the cracks, Crack 1 has the most significant impact on the thermal fatigue life of the solder joint. Under the same thermal cycling conditions, its life has decreased by 46.98%, followed by Crack 2, Crack 4 and Crack 3. On the other hand, under the same random vibration load, Crack 4 has the most significant impact on the solder joint fatigue life, reducing its life by 81.39%, followed by Crack 1, Crack 3 and Crack 2. From the crack propagation direction, with the increase of crack depth, the thermal fatigue life of the SMT solder joint decreases sharply at first and then continues to decline almost linearly. The random vibration fatigue life of the solder joint decreases continuously with the increase of crack depth. From the crack depth of 0.01 mm to 0.05 mm, the random vibration fatigue life decreases by 86.75%. When the crack width increases, the thermal and random vibration fatigue life of the solder joint decreases almost linearly.

Originality/value

This paper investigates the effects of interface cracks on the fatigue life and provides useful information on the reliability of SMT packages.

Details

Microelectronics International, vol. 40 no. 2
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 9 June 2023

Zimou Tang, Min Yang, Jianxiong Xiao, Zheng Shen, Liming Tang and Jibin Wang

This paper aims to present an engineering computational method for fatigue life evaluation of welded structures on large-scale equipment under random vibration load.

Abstract

Purpose

This paper aims to present an engineering computational method for fatigue life evaluation of welded structures on large-scale equipment under random vibration load.

Design/methodology/approach

Based on a case study of the traction transformers, virtual fatigue test (VFT) was proposed via numerical simulation approach. Static analysis was conducted to identify the risky zone and then dynamic response of the risky welds under random vibration load was calculated based on frequency-domain structural stress method (FDSSM) theory, life distribution and associated survivability at various locations of the structure were obtained. Structural modification was finally performed according to the evaluation results. Moreover, experimental test was carried out and compared with the virtual test result.

Findings

By applying the virtual test, fatigue life of the complex welded structures on large-scale equipment can be accurately and efficiently obtained considering dynamic effect under random vibration load. Meanwhile, risky welds can be directly determined and targeted modification scheme can be accordingly concluded. Validity of the VFT result was proved by comparing with the experimental test.

Originality/value

The proposed method can help obtain equivalent structural stress and fatigue life distribution of the welded structure at any position with various survivability and make quantitative evaluation on the life-extending effect of the structural modification. This method shows significant cost and efficiency advantages over experimental test during design stage of the large-scale structures in numerous manufacturing industries.

Article
Publication date: 12 January 2023

Steffany N. Cerda-Avila, Hugo Iván Medellín-Castillo, José M. Cervántes-Uc, Alejandro May-Pat and Aarón Rivas-Menchi

The purpose of this study is twofold: firstly, to investigate the effect of the infill value and build orientation on the fatigue behaviour of polylactic acid (PLA) specimens made…

Abstract

Purpose

The purpose of this study is twofold: firstly, to investigate the effect of the infill value and build orientation on the fatigue behaviour of polylactic acid (PLA) specimens made by fused filament fabrication (FFF), also known as fused deposition modelling; and secondly, to model the fatigue behaviour of PLA specimens made by FFF and similar additive manufactured parts.

Design/methodology/approach

A new methodology based on filament characterisation, infill measuring, axial fatigue testing and fatigue strength normalisation is proposed and implemented. Sixty fatigue FFF specimens made of PLA were fabricated and evaluated using variable infill percentage and build orientation. On the other hand, fatigue modelling is based on the normalised stress amplitude and the fatigue life in terms of number of cycles. In addition, a probabilistic model was developed to predict the fatigue strength and life of FFF components.

Findings

The infill percentage and build orientation have a great influence on the fatigue behaviour of FFF components. The larger the infill percentage, the greater the fatigue strength and life. Regarding the build orientation, the specimens in the up-right orientation showed a much smaller fatigue strength and life than the specimens in the flat and on-edge orientations. Regarding the fatigue behaviour modelling, the proposed Weibull model can predict with an acceptable reliability the stress-life performance of PLA-FFF components.

Research limitations/implications

This study has been limited to axial fatigue loading conditions along three different build orientations and only one type of material.

Practical implications

The results of this study are valuable to predict the fatigue behaviour of FFF parts that will work under variable loading conditions. The proposed model can help designers and manufacturer to reduce the need of experimental tests when designing and fabricating FFF components for fatigue conditions.

Originality/value

A fatigue study based on a novel experimental methodology that considers the variation of the FFF process parameters, the measurement of the real infill value and the normalisation of the results to be comparable with other studies is proposed. Furthermore, a new fatigue model able to predict the stress-life fatigue behaviour of PLA-FFF components considering variable process parameters is also proposed.

Details

Rapid Prototyping Journal, vol. 29 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 6 March 2024

Qiuchen Zhao, Xue Li, Junchao Hu, Yuehui Jiang, Kun Yang and Qingyuan Wang

The purpose of this paper is to determine the ultra-high cycle fatigue behavior and ultra-slow crack propagation behavior of selective laser melting (SLM) AlSi7Mg alloy under…

Abstract

Purpose

The purpose of this paper is to determine the ultra-high cycle fatigue behavior and ultra-slow crack propagation behavior of selective laser melting (SLM) AlSi7Mg alloy under as-built conditions.

Design/methodology/approach

Constant amplitude and two-step variable amplitude fatigue tests were carried out using ultrasonic fatigue equipment. The fracture surface of the failure specimen was quantitatively analyzed by scanning electron microscope (SEM).

Findings

The results show that the competition of surface and interior crack initiation modes leads to a duplex S–N curve. Both manufacturing defects (such as the lack of fusion) and inclusions can act as initially fatal fatigue microcracks, and the fatigue sensitivity level decreases with the location, size and type of the maximum defects.

Originality/value

The research results play a certain role in understanding the ultra-high cycle fatigue behavior of additive manufacturing aluminum alloys. It can provide reference for improving the process parameters of SLM technology.

Details

International Journal of Structural Integrity, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 14 July 2023

Bo Liu, Yue-dong Wang, Zhe Zhang and Qi Dong

This paper aims to study and modify the notch equivalent stress method, as well as to establish the notch equivalent stress range S–N curve and apply it to the fatigue assessment…

Abstract

Purpose

This paper aims to study and modify the notch equivalent stress method, as well as to establish the notch equivalent stress range S–N curve and apply it to the fatigue assessment of engineering examples.

Design/methodology/approach

This paper studies the notch equivalent stress method and puts forward the concept of “singular equivalent crack”. Combined with the fatigue test results, by proposing to consider the singular coefficient of the transition angle of the welded structure and the introduction of material correction factors, this paper derives the notch equivalent stress equation for commonly used welded joints applicable to steel, and finally establishes the notch equivalent stress range of the S–N curve.

Findings

The obtained results show that the dispersion of fatigue data is 65.6 and 75.4% for T-joints and transverse cross-joints, respectively, under S–N curves using notched equivalent stress compared to the nominal stress range. The fatigue evaluation error of the modified notch equivalent stress equation for transverse cross welded joints improved by 50.65%, 53.1 and 39.6% on average, respectively, compared to the original other methods. The fatigue evaluation error for T-joints improved by 13.4 and 13.9%, respectively, compared to the original other methods.

Originality/value

There are relatively few studies on the fatigue assessment of notch equivalent stress method. In this paper, the notch equivalent stress method is studied and modified to improve the accuracy of fatigue assessment of welded structures with singular stresses.

Details

International Journal of Structural Integrity, vol. 14 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 7 November 2023

Shun-Peng Zhu, Xiaopeng Niu, Behrooz Keshtegar, Changqi Luo and Mansour Bagheri

The multisource uncertainties, including material dispersion, load fluctuation and geometrical tolerance, have crucial effects on fatigue performance of turbine bladed disks. In…

Abstract

Purpose

The multisource uncertainties, including material dispersion, load fluctuation and geometrical tolerance, have crucial effects on fatigue performance of turbine bladed disks. In view of the aim of this paper, it is essential to develop an advanced approach to efficiently quantify their influences and evaluate the fatigue life of turbine bladed disks.

Design/methodology/approach

In this study, a novel combined machine learning strategy is performed to fatigue assessment of turbine bladed disks. Proposed model consists of two modeling phases in terms of response surface method (RSM) and support vector regression (SVR), namely RSM-SVR. Two different input sets obtained from basic variables were used as the inputs of RSM, then the predicted results by RSM in first phase is used as inputs of SVR model by using a group data-handling strategy. By this way, the nonlinear flexibility of SVR inputs is improved and RSM-SVR model presents the high-tendency and efficiency characteristics.

Findings

The accuracy and tendency of the RSM-SVR model, applied to the fatigue life estimation of turbine bladed disks, are validated. The results indicate that the proposed model is capable of accurately simulating the nonlinear response of turbine bladed disks under multisource uncertainties, and SVR-RSM model provides an accurate prediction strategy compared to RSM and SVR for fatigue analysis of complex structures.

Originality/value

The results indicate that the proposed model is capable of accurately simulate the nonlinear response of turbine bladed disks under multisource uncertainties, and SVR-RSM model provides an accurate prediction compared to RSM and SVRE for fatigue analysis of turbine bladed disk.

Details

International Journal of Structural Integrity, vol. 14 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

Article
Publication date: 9 January 2024

Shengfu Xue, Zhengping He, Bingzhi Chen and Jianxin Xu

This study investigates the fitting techniques for notch fatigue curves, seeking a more reliable method to predict the lifespan of welded structures.

Abstract

Purpose

This study investigates the fitting techniques for notch fatigue curves, seeking a more reliable method to predict the lifespan of welded structures.

Design/methodology/approach

Building on the fatigue test results of butt and cruciform joints, this research delves into the selection of fitting methods for the notch fatigue curve of welded joints. Both empirical formula and finite element methods (FEMs) were employed to assess the notch stress concentration factor at the toe and root of the two types of welded joints. Considering the mean stress correction and weld misalignment coefficients, the notch fatigue life curves were established using both direct and indirect methods.

Findings

An engineering example was employed to discern the differences between the direct and indirect approaches. The findings highlight the enhanced reliability of the indirect method for fitting the fatigue life curve.

Originality/value

While the notch stress approach is extensively adopted due to its accurate prediction of component fatigue life, most scholars have overlooked the importance of its curve fitting methods. Existing literature scantily addresses the establishment of these curves. This paper offers a focused examination of fatigue curve fitting techniques, delivering valuable perspectives on method selection.

Details

International Journal of Structural Integrity, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1757-9864

Keywords

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