Material Damage Research Articles

GEOTECHNICAL INVESTIGATIONS FOR SCHOOL CONSTRUCTION

A series of earthquakes that commenced on December 28, 2020, resulted in extensive material damage within a 50-60 km radius from the epicenter, located near the City of Petrinja. Due to the significant structural damage sustained by the building of Petrinja Primary School I, a decision was made to construct a new school building. The construction of the new school began in 2022 and was completed in 2023. This study presents the findings of geotechnical investigations conducted at the site of the new school, which included five static cone penetration tests (CPTu), two dynamic probing heavy tests (DPH), one Marchetti dilatometer test (DMT), and two profiles of multi-channel analysis of surface waves (MASW). The geotechnical investigations resulted in the development of a soil profile consisting of eight distinct zones. Recommendations for the foundation design of the new building have been provided, alongside an assessment of the risk of soil liquefaction. The potential for liquefaction has been identified within zone 4, which comprises clayey sands at depths ranging from 4 to 6 meters.

Prediction of Ductile Damage in Composite Material Used in Type IV Hydrogen Tanks by Artificial Neural Network and Machine Learning with Finite Element Modeling Approach

This study investigates the degradation process of composite materials used in high‐pressure hydrogen storage vessels by employing advanced computational techniques. A recurrent neural network, specifically a bidirectional long short‐term memory (Bi‐LSTM) network, is utilized to predict the temporal evolution of ductile damage. The key degradation features are extracted from finite element modeling (FEM) computations using group method of data handling algorithms and treated as time‐series data. Results demonstrate that the Bi‐LSTM network can accurately undergo both elastic and plastic behaviors of the composite under tensile strength. Additionally, traditional machine learning (ML) algorithms such as extreme gradient boosting and random forest are employed to forecast strain degradation, showing promising results. This hybrid approach combining FEM, ML, and deep learning provides a comprehensive method for predicting the degradation of composite materials, offering significant potential for optimizing the design and durability of hydrogen storage vessels.

Prediction of rotational bending fatigue life of bearing steel based on damage mechanics

Based on the theory of continuous damage mechanics, this paper proposes a fatigue damage evolution model and numerical calculation method considering the influence of vacuum chemical heat treatment process, and studies the rotational bending fatigue damage analysis and life prediction method of M50NiL bearing steel. Firstly, the constitutive model, fatigue damage evolution equation and material parameter calibration method in the theoretical model are given. Secondly, based on the ABAQUS platform, the damage mechanics-finite element numerical calculation method of fatigue damage analysis considering the influence of hardened layer is realized by writing the UMAT subroutine; then, the rotational bending fatigue test of M50NiL bearing steel treated by vacuum chemical heat treatment of quenching and tempering, carburizing and carbonitriding is carried out, and the influence of heat treatment process on fatigue performance is analyzed; finally, based on the proposed fatigue damage model and numerical calculation method, the rotational bending fatigue life of M50NiL bearing steel is predicted, and the results are compared with the experimental results to verify the correctness of the proposed method.

Composite delamination damage location based on non-orthogonal air-coupled ultrasonic guided waves and Artifact-Reduction damage index

This study focuses on the localization of delamination damage in composite materials. Due to the attenuation of the air-coupled ultrasound at the gas–solid coupling interface, the signal-to-noise ratio of the air-coupled ultrasonic signal is low, which results in low accuracy of damage detection. This paper proposes a method to locate delamination damage in composite materials. This method uses non-orthogonal Air-coupled Ultrasonic Guided Waves for B-scan; an artifact-reduction damage index (ARDI) is designed with the proportion of the scan paths containing damage information to the entire scan paths. These two exquisite designs improve detection accuracy. Finally, the probability of damage occurrence is calculated, and the detection of the damage location is achieved, with the positioning error of the damage being less than 1.5%.

Effect of external magnetic field on the fretting wear mechanism of the ferromagnetic materials

With the widespread implementation of maglev technology in fields such as rail transit and military, it is imperative to investigate the effects of magnetic fields on fretting damage in metallic materials. This study conducted multi-parameter fretting wear tests on typical ferromagnetic counterparts in the presence of an external permanent magnetic field. Subsequently, the wear behavior and damage mechanism of the fretting interface were elucidated through multi-scale characterization analysis. The results indicated that the operation state of the fretting interface was shifted towards the partial slip regime under the magnetic field. Meanwhile, the external magnetic field transformed the dominant wear mechanism from abrasive wear to adhesive wear. The influence of the external magnetic field on fretting wear has been demonstrated to manifest in dual aspects: Firstly, the Hertzian contact stress at the interface is enhanced by the magnetic field induction force, resulting in a remarkable reduction of about 79.83 % in accumulated dissipation energy; Secondly, the effectiveness of debris being expelled from the worn interface decreased, and the wear progression was further impeded by the accumulated debris, so that the abrasion loss is significantly reduced by about 60.66 %. These findings provide valuable theoretical data and practical reference for the protection of fretting damage in ferromagnetic materials under the action of a magnetic field.

Digital Engineering in Photonics: Optimizing Laser Processing

This article explores the transformative impact of digital engineering on photonic technologies, emphasizing advancements in laser processing through digital models, artificial intelligence (AI), and freeform optics. It presents a comprehensive review of how these technologies enhance efficiency, precision, and control in manufacturing processes. Digital models are pivotal for predicting and optimizing thermal effects in laser processing, thereby reducing material deformation and defects. The integration of AI further refines these models, improving productivity and quality in applications such as micromachining and cladding. Additionally, the combination of AI with freeform optics advances laser technology by enabling real-time adjustments and customizable beam profiles, which enhance processing versatility and reduce material damage. The use of digital twins is also examined as a key development in laser-based manufacturing, offering significant improvements in process optimization, defect reduction, and system efficiency. By incorporating real-time monitoring, machine learning, and physics-based modeling, digital twins facilitate precise simulations and predictions, leading to more effective and reliable manufacturing practices. Overall, the integration of digital twins, AI, and freeform optics into laser processing marks a significant progression in manufacturing technology. These advancements collectively enhance precision, efficiency, and adaptability, resulting in improved product quality and reduced operational costs. The continued evolution of these technologies is expected to drive further advancements in manufacturing practices, offering more robust solutions for complex production environments.

Quantifying the tangential oscillation of thermal stratification by using principal component analysis

Tangential oscillation of thermal stratification is a new finding in previous investigations on thermal-mixing process at pipeline T-junctions. This phenomenon can create regular temperature changes on the pipeline inner surface and lead to material damage caused by the degradation mechanism of thermal fatigue, which has been frequently reported as a reason for incidents in piping systems of nuclear power plants. Previous investigations cannot provide a quantitative description of this phenomenon, making it difficult to understand or evaluate the fatigue potential due to this phenomenon. In this study, a new method namely principal component analysis has been employed for quantitatively estimating the angular shift of the thermal stratification in pipe tangential direction. Time-dependent angular shift is extracted from the temperature data of the transient simulations of the pipe flow and confirms the initiation of the tangential oscillation of thermal stratification. Moreover, a characteristic frequency of approximately 2.3 Hz has been identified from the frequency spectrum of the time-dependent angular shift. It indicates a potential risk in the piping material due to thermal fatigue. Furthermore, results of this study show a high efficiency and accuracy of the principal component analysis method in quantifying tangential oscillation. It can be applied in further investigations of similar phenomena of thermal stratification.

WHITE COLLAR CRIME AS ORGANIZED INSTITUTIONAL CRIME

The object of treatment in this paper is the problem of detection and treatment of corruption. There is no single definition for corruption and in this case it is limited to the corruption practices of white-collar crime, being a link to institutional organized crime, with confirmation of the suspicion of crime in the Prosecutor's Office - especially that of serious crimes which is the main pillar of the state in this right to enforce the law and fight the phenomenon, as well as the state courts. Its meaning is broad and cannot be defined only by accepting or giving a bribe to an official or buying it, as is often practiced. Corruption is often carried out by a highly organized group of people, which gives us elements of institutional organized crime. Since corruption, especially political corruption, is carried out by highly qualified and professional persons, this greatly complicates the operation of the law, detection, investigation, prosecution and judgment of authoritative persons, decision-makers, due to the great powers to hide the traces of corruption and especially the crime of money laundering, being a serious consequence and with great material and moral damage for the citizens of a state. Due to the problems leading to the discovery and proof of this crime and due to the way it is committed, the secret nature, corruption is part of the crimes where the rate of proof is extremely low or even definitely impossible. The work is mainly elaborated on the problems encountered not only by the agencies, the bodies that have a mandate to prevent and fight this negative phenomenon in our society, but also the media and especially the citizens who are involved in harm from authoritative persons and state institutions. A major problem where the citizen there is no address for orientation and when the organized Institutional group usurps the State Institutions and in some form is created as a Mafia group.

Design and analysis of a HTS internally cooled cable for the Muon Collider target and capture solenoid magnets

The Muon Collider is one of the options considered as the next step in High Energy Physics. It bears many challenges, last not least in superconducting magnet technology. The target and capture solenoid is one of them, a channel of approximately 18 m length consisting of co-axial solenoid magnets with a 1.2 m free bore and peak field on axis of 20 T. One of the main concerns come from the nuclear radiation environment that may influence the stable operation of the coil, as well as its material integrity. Energetic photons cause large radiation heat load, of the order of several kW in the cold mass, and deposit a considerable dose, several tens of MGy. Neutrons cause material damage, at the level of 10-3 DPA. These values are at the present limit of superconducting coil technology. We describe here the conceptual design of the target and capture solenoid, focusing on the HTS cable design, which is largely inspired by the VIPER concept developed at MIT. We show how to address margin and protection, cooling and mechanics specific to the HTS cable selected.

Study on the transient cavitation characteristics in an axial flow tandem pump during the rapid starting period

Abstract In axial flow pump systems constrained by limited internal space, the advantages of axial flow tandem pumps are high space utilization, strong power capacity, and great thrust. The onset of cavitation during the rapid starting period poses a classic issue for tandem axial flow pumps, resulting in issues like noise, vibration, cavitation breakdown, and material damage. This article aims to investigate the transient cavitation characteristics of each flow passage component of an axial flow tandem pump during the rapid starting period by numerical simulation method. It is compared that the evolution laws of the cavity of each flow passage component. The evolution of the cavity in all flow passage components is strongly correlated with the flow rate change rate in each stage of the rapid starting period. Among all flow passage components, the first impeller firstly experiences cavitation, and its cavitation severity is also the most severe. The Effective Net Positive Suction Head (NPSHa ) can reduce the influence of transient effects on cavity prediction and better characterize the details of the cavity evolution in different impellers than the cavitation number σ during the rapid starting period. Meanwhile, The NPSHa of the second impeller inlet is always higher than that of the first impeller inlet, indicating superior cavitation performance for the second impeller.

Longitudinal torsional ultrasonic vibratory assistant milling of borosilicate glass material removal mechanism based on the thickness of undeformed chips

Borosilicate glass is an ideal material for microfluidic chip substrates due to its excellent light transmittance and stable chemical properties. However, it is also prone to brittle fracture during processing, making it a typical difficult-to-machine material. As an emerging processing technology, longitudinal torsional ultrasonic assistant milling (LTUVAM) can effectively reduce the surface damage of glass materials and improve the proportion of plastic removal of materials. The mechanism of LTUVAM of borosilicate glass was studied in this paper. Critical undeformed chip thickness (hc) is a key factor in achieving plastic material removal. At present, the influence of LTUVAM on the hc is not clear. Therefore, in this paper, the material-specific cutting energy model in the LTUVAM process was established to predict the hc. Firstly, the motion path of LTUVAM was analyzed, and the undeformed chip thickness model and the tool-workpiece separation rate model were established. Then, based on the above model, the material-specific cutting energy model was established according to the material removal principle. Finally, an LTUVAM orthogonal experiment was carried out to study the surface quality of the material. The experimental results showed that with the increase of ultrasonic power, the roughness and side damage area increased first and then decreased. With the increase of spindle speed, it showed that the roughness and side damage area decreased first and then increased. With the increase of feed per tooth, it showed that the roughness increased first and then decreased, and then increased, and the side damage area increased first and then decreased. Through the analysis of the experimental and model results, the increase of the separation rate between the tool and the workpiece contributes to the increase of the hc and the improvement of the processing quality.

Damage and removal behaviors of indium phosphide crystals involved in ultrasonic vibration-assisted AFM machining

Indium phosphide (InP) crystals exhibit a propensity for brittle damage during machining, categorizing them as challenging materials due to their inherent brittleness and pronounced anisotropy. Atomic force microscopy (AFM) machining serves as a crucial approach for achieving low-damage removal of such brittle crystals. Molecular dynamics simulations were conducted to investigate the vibration-assisted AFM machining of InP crystals, systematically exploring the effects of scratching force, stress distribution, and subsurface damage. The findings revealed that plastic deformation of InP crystals during vibration-assisted AFM scratching was primarily governed by mechanisms including stress-induced amorphization transitions, phase transformations, dislocations, stacking faults, and lattice distortions. Compared to conventional AFM machining, vibration-assisted AFM machining had a smaller average contact area and maintained a periodic movement pattern of contact-separation. This induced the change of chip removal from piling up in front of the cutting tool to uniform flow to both sides. Employing appropriate vibration parameters in vibration-assisted AFM significantly diminished the scratching force, stress, dislocation length, and subsurface damage depth. These results not only elucidate the material removal and damage mechanisms of InP crystals at atomic and close-to-atomic scales, but also offer theoretical guidance for parameter optimization in the vibration-assisted AFM machining of other soft and brittle crystals.

Dynamic mixing characteristics of a soft elastic tubular reactor (SETR): Experimental investigation and numerical simulation

In an innovative effort to mitigate material damage and enhance overall mixing performance, the use of a soft elastic tubular reactor (SETR) was explored. In this study, the mixing of tracer in SETR was observed with the help of non-invasive method. The effect of different parameters such as pusher squeezing frequency (F), distance between pushers (D) and pusher squeezing mode (M) on the flow field inside the SETR was also analyzed with the help of numerical simulations. The study also further optimized the operating parameters of the reactor. The experimental results proved the accuracy of the subsequent simulation model. Through the combination of response surface design and numerical simulation methods, it was found that all three factors have a significant effect on the mixing time. The results of this work add to our understanding of the mixing mechanism within SETR and present new opportunities for designing highly efficient industrial reactors.

MT-CrackNet:A multi-task deep learning framework for automatic in-situ fatigue micro-crack detection and quantification

Characterizing fatigue micro-cracks is crucial for understanding the mechanisms and behaviors of material damage. In-situ fatigue testing is an essential method for observing the evolution of fatigue micro-cracks; however, the process often requires significant time, making the measurement of micro-cracks a tedious task. This paper introduces a multi-task deep learning framework called MT-CrackNet, which enables automatic detection and quantification of in-situ fatigue micro-cracks. The framework is capable of recognizing or segmenting multiple tasks such as micro-cracks, text, and scales simultaneously, and its effectiveness is not limited by the magnification of in-situ images. By integrating attention mechanisms and multi-scale strategies, the model enhances its ability to handle long-range dependencies and preserve detail information, accurately identifying and measuring the length of micro-cracks. The effectiveness of the proposed MT-CrackNet is validated through three in-situ fatigue micro-crack propagation experiments.

Experimental testing and plastic strain analysis of high strength steel longitudinal plate to tubular X joints

Applying high strength steels to tubular joints can increase the propensity to fracture failure due to their lower ductility. However, to simulate the fracture behavior in the finite element (FE) analysis, sophisticated material damage model with rigorous fracture criteria should be incorporated. Recently, the latest draft of ISO 14346 has advocated the use of 5% strain limit in FE analysis of tubular joints. The strain limit concept has been further developed by the authors’ previous work, for its use as a practical alternative to the complicated material damage model. Specifically, a lowered limit of 2.5% was recommended for longitudinal plate to circular hollow section (CHS) joints subjected to in-plane bending. This study extends the strain limit investigation to longitudinal plate to tubular X joints subjected to tensile loads. An experimental program is first presented which included both CHS and rectangular hollow section (RHS) chord members fabricated from two high strength steels with nominal yield stresses of 460 MPa and 700 MPa. Based on test-validated supplemental numerical analyses, it is suggested that the joint load corresponding to 2.5% strain limit can be taken as the load-bearing capacity to suppress occurrence of a fracture failure for the tubular joint configurations considered in this study.

Material removal and damage formation mechanisms induced by periodic indentation during ultrasonic vibration-assisted scratching of SiCf/SiC composites

Fiber-reinforced ceramic matrix composites (CMCs) exhibit high hardness, brittleness, heterogeneity, and anisotropy. This study explores the material removal and damage formation mechanisms during ultrasonic vibration-assisted scratching of SiCf/SiC composites through experimental and micro-finite element simulations. The research reveals that high-frequency periodic indentation-separation of abrasive grain influences stress transfer and crack propagation, which are affected by the interfacial layer and fiber orientation. Crack deflection plays a crucial role in material removal and determines the amplitude of normal scratching force. Stress transfer interference primarily governs damage formation, with more severe damage occurring along the longitudinal and transverse fiber directions due to secondary stress concentration and crack deflection. In contrast, scratching along the perpendicular fiber direction requires higher normal forces due to residual adjacent phase materials, but results in more controlled material removal and less damage. The study provides insights into optimizing the ultrasonic vibration-assisted machining of CMCs to minimize damage.

Investigation of Clinical Features and Comorbid Psychopathologies of Children with Sleep Terrors

Aim: In this study, it was aimed to investigate the clinical characteristics of children diagnosed with sleep terrors, including sleep environment and sleep habits, clinical features and comorbid psychiatric disorders. Method: Between 2020 and 2024, 51 children who were diagnosed with sleep terror according to DSM-5 diagnostic criteria in 3 different Child and Adolescent Psychiatry clinics were included in the study. The sociodemographic and clinical characteristics of the cases were examined retrospectively through the files. Results: Of the 51 participants, 30 (58.8%) were male, 21 (41.2%) were female and the mean age at the time of admission was 6.76±1.45 years. It was determined that 15 (29.4%) of the cases slept in a noisy environment and 41 (80.4%) of the cases had their sleep interrupted except for sleep terror attacks. At least one psychiatric disorder was detected in 17 (33.3%) patients, and the most common (9.8%) comorbid psychiatric disorder was attention deficit hyperactivity disorder. It was found that complete retrograde amnesia was significantly higher in preschoolers, and motor activity during the attack, physical injury and/or material damage, and full awakening during the attack were significantly higher in school-age children. It was determined that 64.7% of the parents intervened incorrectly during the episode, and in 29.4% of the cases, the wrong medication was applied in the treatment history. Conclusion: In sleep terrors, identification of triggering factors and comorbid psychiatric disorders during the diagnostic evaluation process, psychoeducation of parents in treatment, and selection of appropriate medication for medication are very important.

The Civil Law Aspects of Informed Consent to Medical Procedures

Introduction: Informed consent is a communication process between healthcare providers and patients regarding the medical procedures to be performed. Its aim is to provide sufficient information so that patients can make informed decisions, and it is regulated by various laws and regulations in Indonesia.Purpose of the Research: The purpose of this research is to analyze the legal position of informed consent from the perspective of Indonesian civil law and to examine the civil law implications that arise if there is a violation of the informed consent principle in medical procedures.Method of Research: This research uses normative legal methods with legislative and conceptual approaches, analyzing primary, secondary, and tertiary legal materials through literature study, and applying descriptive qualitative analysis.Results of Research: Research findings indicate that informed consent holds a strong legal position within the perspective of Indonesian civil law, being viewed as a manifestation of a therapeutic agreement that must meet the valid agreement requirements according to the Civil Code (KUHPerdata) and be supported by various regulations. Violations of the principles of informed consent can lead to significant civil legal implications, including claims for damages on the grounds of breach of contract or unlawful acts, cancellation of the therapeutic agreement, liability for breach of professional standards, and claims based on consumer protection law. These implications can involve healthcare professionals and healthcare institutions, with consequences that include payment of material and immaterial damages, the burden of proof in court, and impacts on reputation and medical practice.

Investigation of Dust Explosion in Food Silos: A Review

In this article, dust explosion phenomena and the status of research conducted on silos are reviewed. Dust explosions cause loss of life and property in many industrial facilities. There are many recorded dust explosion cases in our country as well as in the world. For example, in our country, in 2023, a dust explosion occurred in the TMO Kocaeli General Directorate (Derince Port Silo), in which 2 people died and great material damage occurred, as reflected in the national press. When we look at the various dust explosion cases that have occurred in the world, it is understood that they mostly occur in silos used for storage in the agricultural and food sectors. Licensed warehouses have been established in many regions of our country in order to store basic and processed agricultural products that can be standardized with the Agricultural Products Licensed Warehousing Law No. 5300, which came into force after being published in the Official Gazette on 17/02/2005, in safe and healthy conditions in warehouses belonging to licensed warehouse enterprise and continues to be established. It is important to understand the many factors affecting dust explosion, such as dust dispersion, properties, discharge, etc., and to design silos according to these factors. These effects are tried to be determined and understood through experimental or CFD simulations.

Salt-freeze resistance and life prediction of geopolymer recycled concrete mixed with rice husk ash and modified rubber particles

Rice husk ash (RHA) and Span-40 modified waste rubber particles (WRP) were mixed into geopolymer recycled concrete (GRC) to improve its frost resistance in normal and chlorine environment. The freeze-thaw and static loading test results show that GRC has the best freeze-resistance when 5 %RHA and 10 %WRP are added. The strength loss rate of GRC after 200 freeze-thaw cycles in normal environment and chlorine salt environment is 8.3 % and 8.8 % lower than that of GRC without RHA and modified WRP, respectively. Based on the test results, the material damage model and strength loss model of GRC doped with RHA and modified WRP were established. The failure probability and service life of GRC were predicted. The results showed that the failure probability of GRC mixed with 5 %RHA and 10 %WRP was reduced by more than 10 % compared with that of GRC mixed with no RHA and modified WRP at 200 freeze-thaw cycles under normal environment and chlorine salt environment, and the failure probability decreased with the increase of cycle times. The life prediction results showed that the service life of GRC mixed with 5 %RHA and 10 %WRP increased by 17.9 % and 21.6 %, respectively, compared with that of GRC mixed with no RHA and modified WRP under the freeze-thaw cycle of normal environment and chlorine salt environment.