Papers by Keyword: Crack Propagation

Abstract: Silicon carbide (SiC), a representative of next-generation wide-bandgap semiconductors, exhibits enormous application potential in fields such as new energy vehicles, aerospace, and photovoltaic power generation. Conventional cutting methods based on diamond wire sawing suffer from high material loss and are prone to causing fractures. In contrast, laser slicing, as a kerf-free processing technology, enables the acquisition of high-quality wafers with minimal material removal. This study systematically investigates the effect of processing cycles on crack propagation and delamination strength during laser slicing of SiC. The experimental results demonstrate that under optimized parameters, an appropriate number of processing cycles can achieve successful wafer separation while maintaining surface integrity, reducing material loss, and lowering delamination strength. The established processing window provides practical guidance for improving SiC slicing quality and holds significant implications for advancing innovative wafer manufacturing technologies in power electronics applications.

Abstract: This study investigates the mechanical properties and crack propagation behavior of 3D-printed Acrylonitrile Butadiene Styrene (ABS) by integrating numerical simulations with experimental tensile testing. Utilizing the eXtended Finite Element Method (XFEM) within the Abaqus software, the research examines the damage evolution in ABS specimens under Mode I loading, focusing on the influence of factors such as print orientation, infill density, and layer thickness on mechanical performance. The numerical model, validated through uniaxial tensile tests conducted at a rate of 10 mm/min on ABS specimens with an initial notch, accurately captures the crack propagation process, revealing a two-stage fracture evolution: an initial stable phase over the first 60% of the specimen’s lifetime, followed by rapid crack growth leading to structural failure. Three distinct phases of crack propagation velocity are identified: low velocity during initiation, a quasi-static intermediate phase, and a high-velocity unstable phase, correlating with the evolution of the stress intensity factor. The close agreement between numerical and experimental results underscores the reliability of XFEM for modeling crack behavior, providing critical insights into optimizing 3D printing parameters to enhance the mechanical properties, structural integrity, and durability of ABS components for diverse engineering applications.

Abstract: This study presents an atomistic analysis of the stress-strain characteristics in the laser powder bed fusion (LPBF) process for the AlSi10Mg alloy. The stress-strain response of printed components is investigated by introducing defects through molecular dynamics simulation. The simulation box dimensions for tensile tests and crack propagation are 152.416 Å, 201.228 Å, and 42.49 Å along the X, Y, and Z directions. Periodic boundary conditions are applied along all sides. A constant strain rate of 10⁹ s⁻¹ is applied along the Y-direction at a temperature of 300 K. The simulation results reveal that the maximum stress occurs at the initial time step, followed by a gradual decline as stress decreases and strain increases, indicating plastic deformation through dislocation slip. Dislocation Analysis (DXA) shows that dislocations increase with increasing strain. These findings enhance the understanding of the material's deformation behaviour and provide insights for optimizing its properties through laser processing parameters.

Abstract: Reliable fretting fatigue prediction requires rigorous evaluation of analytical methods under realistic loading conditions. This study builds upon previous research on the fretting fatigue behavior of 42CrMo4+QT steel by incorporating new experimental data from square cross-section specimens tested under axial loading with various pad geometries. The application of a non-zero tensile mean bulk load promoted localized crack initiation near the specimen edges, leading to more asymmetric crack growth in the majority of cases unlike the more symmetric behavior observed under fully reversed loading (R = –1). Finite element analysis (FEA), along with the Dang Van and Papuga QCP methods, was employed to evaluate whether this behavior could be accurately modeled. In addition, a linear-elastic fracture mechanics approach was used to model and explain these observations. Furthermore, fretting fatigue tests on 34CrNiMo6+QT steel revealed that tribological effects governed crack initiation, in contrast to the stress-driven failure observed in 42CrMo4+QT. These findings enhance understanding of fretting fatigue mechanisms and improve predictive modeling approaches.

Abstract: Woven glass fibre-reinforced polymer composite materials are widely used in different sectors, replacing traditional construction materials with their advantages in lightweight construction, high strength-to-weight ratio, etc., and especially their ability to impart transverse stiffness to the structure. The objective of the current investigation is to introduce a side edge notch to the laminate and study the failure pattern. The effect of crack length on the failure pattern and strength of the laminate is also studied here using the extended Finite Element Method (XFEM). Maximum stress criteria based on bilinear traction separation law are utilised for crack initiation, and critical energy release criteria are used for crack opening and propagation. The results show the effectiveness of XFEM in capturing failure patterns in the laminate for all the considered cases.

Abstract: The purpose of this study is to explore the effect of groove angle on the fatigue life of high-speed train brake discs. A thermal-mechanical coupling model of high-speed train brake discs with different angles (0°, 22.5°, 45°, 67.5°, and 90°) was designed and established. The effects of different groove angles on temperature and stress were studied and analyzed. Experimental specimens were prepared using special processing methods, and friction and wear characteristics experiments were carried out to further verify the simulation results. At the same time, based on the above results, life models of brake discs with different groove angles were established to study the effect of the angle on their fatigue life. Stress has a direct impact on the crack initiation life of groove brake discs, and temperature changes affect the material properties of brake discs, thereby affecting the crack initiation time. The crack growth life of 0° groove brake discs is longer, while the crack growth life of brake discs with other groove angles decreases as the groove angle decreases. Compared with the 0° groove angle, the crack propagation life of the 45° groove angle accounts for approximately 84.7%, while that of the 22.5° groove angle accounts for approximately 80.4%. These research results provide a theoretical basis and numerical research methods for the design of brake disc structures.

Abstract: The thickness of the adhesive has a major influence on the shear strength of bonded assemblies. This work is based on a study of the fatigue behavior of two cracked aluminum (2024 T351) plates repaired by patch (graphite/epoxy) under cyclic loading. For this we used a computer code to study the propagation of fatigue cracks to predict the life of the plates repaired named AFGROW. The first plate was repaired using an adhesive made from date palm waste whereas the second plate was repaired using FM-73 adhesive. The results obtained from this study show that, despite the low shear modulus of the adhesive made from date palm waste and the very low film thickness, the joint bonded with the latter gives good joint strength and a lifetime (number of cycles) similar to the joint bonded with the FM-73 adhesive when the thickness of the joint of the adhesive is greater than that of the adhesive made by the waste of the date palm. This shows that the strength of the bonded joint increases rapidly from very low thicknesses (less than a few hundredths of a millimeter). Finally, we recommend using the adhesive made from date palm waste for patch repair as well as for applications such as lightweight construction, electric vehicles or solar panels.

Abstract: A significant number of high-performance engineering structures are repeatedly subjected to both thermal and mechanical loads, often in a combined fashion. However, because of the increase in the plasticity of metallic structures when they are loaded at high temperatures, the analysis become very complex. This presents a significant obstacle for the comprehension of both the growth of cracks and the thermo-mechanical fatigue performance of the material. Thermomechanical fatigue and thermal fatigue are characterized by external and internal constraining forces, respectively. The beginning and spread of thermal fatigue cracks are controlled by a variety of factors, including the modes of heating and cooling, the temperature range, the maximum temperature rates, and the holding times. The process of a crack beginning and the rate at which it spreads are both sped up when the temperature is raised. However, because of the development of powerful statistical learning algorithms as well as rapid advancements in computational power, there has been an increased adoption of machine learning approaches as well as other advanced computational analyses and numerical software for crack damage detection and damage severity. This has led to an increase in the use of these methods.

Abstract: In this work, a new type of δ-TRIP steel was designed. The fatigue limit and S-N curve were measured by the fatigue testing machine. The fatigue fracture was observed by the scanning electron microscope (SEM), and influencing factors of fatigue crack initiation were analyzed. The results show that the fatigue limit of δ-TRIP steel is 361MPa, and fatigue cracks are initiated on the surface of the sample. In the initial stage of fatigue crack initiation, the crack growth rate of the specimen is relatively slow under the action of stress. As the crack continues to expand, the magnitude and direction of the stress on the crack tip change and the stress situation becomes more complicated. The crack begins to branch and grows in different directions The metastable retained austenite in δ-TRIP steel undergoes phase transformation under the action of external force, which will absorb a lot of energy. At the same time, there are many large angle grain boundaries in the steel hindering the crack propagation. These two characteristics make the δ-TRIP steel has excellent fatigue performance.

Abstract: The model widely used in the fatigue crack growth study in materials science and fracture mechanics is the Paris-Erdogan, which relates the stress intensity factor with the subcritical crack growth, under a fatigue regime. In this work, a seven degree polynomial is used as an alternative to model the crack propagation behavior and to be able to analyze the three regions charts of the cycles by load, in contrast to the common model that it performs at a slight approximation of the propagation phase of the trinca (region II). Finally, a comparison has been made between the proposed model and the secant method by the ASTM 647,2000 standard that adjusts the points obtained experimentally. This proposed equation is new as another alternative analytical model for which the adjustment parameter “R” are compared in relation to the classical approach in a aeronautical ABNT 4130 steel.