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3 pages, 160 KiB

Open AccessEditorial

Fatigue Strength of Machines and Systems

by Przemysław Strzelecki, Michał Stopel and Maciej Kotyk

Appl. Sci. 2025, 15(8), 4510; https://doi.org/10.3390/app15084510 - 19 Apr 2025

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Abstract

Fatigue properties have been a topic of investigation since the nineteenth century [...] Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

Research

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29 pages, 15135 KiB

Open AccessArticle

Fatigue Analysis of 3D-Printed Materials for Temporary Reconstructions on Dental Implants—A Pilot Study

by Adam Nowicki, Karina Krawiec, Karolina Osypko, Adam Kurzawa, Mateusz Stachowicz, Piotr Kotowski and Dariusz Pyka

Appl. Sci. 2025, 15(6), 3212; https://doi.org/10.3390/app15063212 - 15 Mar 2025

Viewed by 586

Abstract

The rapid development of 3D printing technology has enabled its application in many fields, including dentistry. One of the key applications is temporary prosthetic restorations on dental implants, used during the osteointegration process. These restorations provide functionality and aesthetics, but their durability under [...] Read more.

The rapid development of 3D printing technology has enabled its application in many fields, including dentistry. One of the key applications is temporary prosthetic restorations on dental implants, used during the osteointegration process. These restorations provide functionality and aesthetics, but their durability under oral conditions exposed to dynamic loads remains a challenge. This pilot study evaluated the thermal expansion and fatigue resistance of three commercially available photopolymer materials used in 3D printing: NextDent Denture 3D, NextDent C&B MFH Bleach, and Graphy TC-80DP. Thermal expansion and dimensional stability analyses were performed on samples subjected to cyclic heating and cooling. Fatigue tests were designed to evaluate the behaviour of the materials under repetitive mechanical loads mimicking chewing. Microscopic analyses (SEM) made it possible to identify the internal structure of the materials and their damage mechanisms. The results showed that the tested materials have a low coefficient of thermal expansion and high dimensional stability after cyclic heating and cooling. However, significant differences were observed in their mechanical properties and fatigue resistance. The best results were obtained for the Graphy TC-80DP material, while NextDent Denture 3D showed the least resistance to cyclic loading. NextDent Denture 3D exhibited the highest thermal expansion coefficient (123.6 × 10⁻⁶/K), while Graphy TC-80DP showed the lowest (83.9 × 10⁻⁶/K), ensuring better dimensional stability. Fatigue tests revealed that Graphy TC-80DP withstood up to 675,221 cycles at 51 MPa, while NextDent Denture 3D failed after 420 cycles. SEM analysis confirmed that Graphy TC-80DP maintained structural integrity longer, while NextDent Denture 3D exhibited early crack propagation. This study fills a gap in the knowledge of the behaviour of dental materials produced with 3D printing technology under real-world conditions and provides a basis for further, more advanced research to improve their properties and patient comfort. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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11 pages, 823 KiB

Open AccessArticle

Methodology to Determine the Stress Distribution Based on Fatigue Data with Bilinear Behavior and Its P–S–N Field and Testing Plan

by Osvaldo Monclova-Quintana, Manuel R. Piña-Monarrez, María M. Hernández-Ramos and Jesús F. Ortiz-Yáñez

Appl. Sci. 2025, 15(5), 2295; https://doi.org/10.3390/app15052295 - 21 Feb 2025

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Abstract

In this paper, based on the Weibull Inverse Power Law, we present a methodology to determine the following: (1) the failure percentiles, referred to as the P–S–N field, of an S–N curve for a 42CrMo4 steel material exhibiting bilinear ( [...] Read more.

In this paper, based on the Weibull Inverse Power Law, we present a methodology to determine the following: (1) the failure percentiles, referred to as the P–S–N field, of an S–N curve for a 42CrMo4 steel material exhibiting bilinear (

s_{1} and s_{2})

behavior (e.g., a competence failure mode); (2) the Weibull family that characterizes the entire bilinear behavior; and (3) the zero-vibration test plan that meets the required vibration reliability index of

R (t) = 0.97

with a reliability confidence level of

C L = 0.75

. From the application, based on the formulated normal–Weibull relationship, we determine the failure percentiles for the normal (one, two, and three) sigma levels, as well as those failure percentiles corresponding to the capability (

C p

) and ability (

C p k

) indices. Finally, we present the formulation to determine the

R (t)

index and the

C L

level associated with each normal percentile, along with their numerical values. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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18 pages, 2931 KiB

Open AccessArticle

Influence of Nonstationary Processes in Drill Rigs on the Durability of Structural Elements

by Yevhen Kharchenko, Yaroslav Blikharskyy, Andriy Bilovus, Volodymyr Vira, Jacek Selejdak and Zinoviy Blikharskyy

Appl. Sci. 2024, 14(13), 5930; https://doi.org/10.3390/app14135930 - 7 Jul 2024

Viewed by 1382

Abstract

Assessing the effects that nonstationary dynamic processes have on the durability of structural elements belongs to an important trend in modern dynamics and technical diagnostics of machines. Normally, fatigue strength calculations are performed taking into account only periodically variable stresses, as steady operating [...] Read more.

Assessing the effects that nonstationary dynamic processes have on the durability of structural elements belongs to an important trend in modern dynamics and technical diagnostics of machines. Normally, fatigue strength calculations are performed taking into account only periodically variable stresses, as steady operating modes of machines are much longer in comparison with transient modes. However, a significant role in fatigue failure in machines and engineering structures is also played by nonstationary loads. This is explained by emerging intensive oscillations in the mechanical system during accelerating, braking, or changing the operation mode of a machine unit, which often lead to the accumulation of fatigue damages in the materials of parts in heavy loaded assemblies. The combination of stationary and nonstationary dynamic loads manifests itself, particularly in drilling rigs, where technological cycles include steady motion modes, starts, and stops. This paper represents a generalized mathematical model describing nonstationary processes in the lift system of a drill rig, which considers the relationship between electromagnetic processes in asynchronous motors and mechanical oscillatory phenomena, with the purpose of determining dynamic loads and stresses in structural elements of the rigs. Nonlinear physical systems include mechanical members with both concentrated and clearly expressed distributed parameters. The durability of structural elements is evaluated by means of a computer algorithm for analysis of crack growth rates using the NASGRO equation obtained with the presence of plastic deformation zones. An example of the crown block axis illustrates the influence of nonstationary dynamic processes in drill rigs on the durability of structural elements. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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9 pages, 1788 KiB

Open AccessArticle

Evaluation of the Technical Condition of Pipes during the Transportation of Hydrogen Mixtures According to the Energy Approach

by Yaroslav Ivanytskyi, Yaroslav Blikharskyy, Jarosław Sęp, Zinoviy Blikharskyy, Jacek Selejdak and Oleh Holiian

Appl. Sci. 2024, 14(12), 5040; https://doi.org/10.3390/app14125040 - 10 Jun 2024

Cited by 1 | Viewed by 1063

Abstract

In this study, a theoretical–experimental methodology for determining the stress–strain state in pipeline systems, taking into account the hydrogen environment, was developed. A complex of theoretical and experimental studies was conducted to determine the specific energy of destruction as an invariant characteristic of [...] Read more.

In this study, a theoretical–experimental methodology for determining the stress–strain state in pipeline systems, taking into account the hydrogen environment, was developed. A complex of theoretical and experimental studies was conducted to determine the specific energy of destruction as an invariant characteristic of the material’s resistance to strain at different hydrogen concentrations. The technique is based on the construction of complete diagrams of the destruction of the material based on the determination of true strains and stresses in the local volume using the method involving the optical–digital correlation of speckle images. A complex of research was carried out, and true diagrams of material destruction were constructed, depending on the previous elastic–plastic strain and the action of the hydrogen environment. The change in the concentration of hydrogen absorbed by the material was estimated, depending on the value of the specific energy of destruction. A study was conducted on tubular samples, and the degree of damage to the material of the inner wall under the action of hydrogen and stress from the internal pressure was evaluated according to the change in specific energy, depending on the value of the true strain established with the help of an optical–digital correlator on the outer surface, and the degree of damage was determined. It has been established that the specific fracture energy of 17G1S steel decreases by 70–90% under the influence of hydrogen. The effect of the change in the amount of strain energy on the thickness of the pipe wall is illustrated. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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24 pages, 13244 KiB

Open AccessArticle

Upgrade of the Universal Testing Machine for the Possibilities of Fatigue Tests in a Limited Mode

by Róbert Huňady, Peter Sivák, Ingrid Delyová, Jozef Bocko, Ján Vavro, Jr. and Darina Hroncová

Appl. Sci. 2024, 14(10), 3973; https://doi.org/10.3390/app14103973 - 7 May 2024

Cited by 2 | Viewed by 2117

Abstract

The object of the upgrade presented in this paper was an older analogue-based universal testing machine preferably designed for tensile testing. The objective of the upgrade was to create a new digitized measurement chain capable of also operating in the mode of simple [...] Read more.

The object of the upgrade presented in this paper was an older analogue-based universal testing machine preferably designed for tensile testing. The objective of the upgrade was to create a new digitized measurement chain capable of also operating in the mode of simple fatigue tests with cyclic tensile stresses. The upgrade of the equipment mainly included the processes of calibration, creation of related calibration jigs, creation of transformation dependencies and digitization, creation or completion of missing parts of chain-signal conditioning modules, A/D converters, special jigs, etc., as elements of the experimental hardware. The degree of correctness of the calibration and of the transformation dependencies created was verified by regression analysis, and this was verified by simple correlation analysis. The correctness of the proposed modifications, was verified on the basis of the fatigue tests performed for cyclic loading. Thus, it was possible to design, develop and functionally verify a new measurement chain based on an older universal testing machine. Thus, a partially digitized pulsator was created for the possibility of fatigue testing in a technically or functionally limited mode, mainly for educational purposes as a temporary replacement for the order of magnitude more expensive commercially produced test systems. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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17 pages, 5590 KiB

Open AccessArticle

Unconventional Wells Interference: Supervised Machine Learning for Detecting Fracture Hits

by Guoxiang Liu, Xiongjun Wu and Vyacheslav Romanov

Appl. Sci. 2024, 14(7), 2927; https://doi.org/10.3390/app14072927 - 30 Mar 2024

Cited by 2 | Viewed by 1621

Abstract

The primary objective of the study was development of a machine learning (ML)-based workflow for fracture hit (“frac hit”) detection and monitoring using shale oil-field data such as drilling surveys, production history (oil and produced water), pressure, and fracking start time and duration [...] Read more.

The primary objective of the study was development of a machine learning (ML)-based workflow for fracture hit (“frac hit”) detection and monitoring using shale oil-field data such as drilling surveys, production history (oil and produced water), pressure, and fracking start time and duration records. The ML method takes advantage of long short-term memory (LSTM) and multilayer perceptron (MLP) neural networks to identify the frac hits due to hydraulic communication between the fracking child well(s) and the producing parent well(s) within the same pad (intra-pad interaction) and/or on different pads (inter-pad interaction). It utilizes time series of pressure and production data from within a pad and from adjacent pads. The workflow can capture time variable features of frac hits when the model architecture is deep and wide enough, with enough trainable parameters for deep learning and feature extraction, as demonstrated in this paper by using training and testing subsets of the field data from selected neighboring pads with over a couple of hundred wells. The study was focused on frac-hit interaction among paired wells and demonstrated that the ML model, once trained, can predict the frac-hit probability. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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13 pages, 2867 KiB

Open AccessArticle

Determination of the Statistical Power of Fatigue Characteristics in Relation to the Number of Samples

by Przemysław Strzelecki and Janusz Sempruch

Appl. Sci. 2024, 14(6), 2440; https://doi.org/10.3390/app14062440 - 14 Mar 2024

Viewed by 1165

Abstract

The paper presents guidelines included in the ISO 12107:2003 standard regarding the number of samples for determining the fatigue characteristics in the high cycle range. The proposed normative values were compared with the classical statistical approach. Fatigue test results for S355J2+C steel for [...] Read more.

The paper presents guidelines included in the ISO 12107:2003 standard regarding the number of samples for determining the fatigue characteristics in the high cycle range. The proposed normative values were compared with the classical statistical approach. Fatigue test results for S355J2+C steel for rotary bending were used for verification. In addition, the error and power of a statistical test were determined for characteristics with different sample sizes. It determined the number of specimens to estimate the fatigue curve, which required significant error and power of the statistical test. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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14 pages, 991 KiB

Open AccessArticle

Study on Load Distribution and Fatigue Elastic Life of Ball Screw under Ultimate Conditions

by Lei Lv, Changhou Lu, Shujiang Chen and Weike Wang

Appl. Sci. 2024, 14(5), 1966; https://doi.org/10.3390/app14051966 - 28 Feb 2024

Cited by 2 | Viewed by 1384

Abstract

When subjected to extreme loads and ultra-low cycling conditions, the primary mode of failure in a ball screw is that excessive plastic contact deformation of the raceway surface exceeds acceptable limits. Consequently, traditional fatigue life theories based on pitting fatigue are not applicable [...] Read more.

When subjected to extreme loads and ultra-low cycling conditions, the primary mode of failure in a ball screw is that excessive plastic contact deformation of the raceway surface exceeds acceptable limits. Consequently, traditional fatigue life theories based on pitting fatigue are not applicable in this context. This study evaluated the load distribution within the ball screw, considering factors such as the nut position and screw length. The plastic deformation of the raceway surfaces is analyzed using Thornton’s elastoplastic theory. Furthermore, this paper integrates the concepts of plastic deformation and fatigue elastic life to investigate the fatigue elastic life of ball screws under extreme conditions. To validate the proposed approach, the calculated results are compared with those from previous experimental studies, confirming its effectiveness. When the ratio of the nut position to the screw length approaches 0.7, the fatigue elastic life of the ball screw achieves its maximum. An increase in screw length, load, or raceway conformity ratio leads to a decrease in fatigue elastic life. Conversely, an increase in contact angle and ball diameter enhances the fatigue elastic life. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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20 pages, 9943 KiB

Open AccessArticle

Study on the Residual Strength of Nonlinear Fatigue-Damaged Pipeline Structures

by Wenlan Wei, Rui Zhang, Yuwen Zhang, Jiarui Cheng, Yinping Cao and Fengying Fang

Appl. Sci. 2024, 14(2), 754; https://doi.org/10.3390/app14020754 - 16 Jan 2024

Cited by 1 | Viewed by 1335

Abstract

The heat alternation and bending during the service process of the pipeline structure are the key issues affecting its residual strength. The nonuniform plastic deformation of its cross-section causes nonlinear damage to the structure, which makes it difficult to calculate the residual strength [...] Read more.

The heat alternation and bending during the service process of the pipeline structure are the key issues affecting its residual strength. The nonuniform plastic deformation of its cross-section causes nonlinear damage to the structure, which makes it difficult to calculate the residual strength of the overall structure. This study proposed a novel variable-strength material damage model with damage accumulation, which achieved the coupling analysis of structural damage and material fatigue residual strength, making the structural strength of nonlinear damage cross-section computable. Based on this, a theoretical ultimate load model for nonlinear damage cross-section and a finite element analysis model for dynamic material strength with damage accumulation were established. The analysis was conducted on the repeated banding damage to coiled tubing. The results showed that the residual yield strength of nonlinear damaged coiled tubing showed a trend of first rapid decrease and then slow decrease with damage accumulation, and the tensile displacement showed an increasing trend with damage accumulation. The ultimate internal pressure strength of nonlinear damaged structures showed a similar downward trend to the yield strength. The nonlinear damage coupling analysis model proposed in this study has significant practical engineering application value. Full article

(This article belongs to the Special Issue Fatigue Strength of Machines and Systems)

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