Effects of Interlayer Resin Bonding on Fatigue Crack Initiation/Propagation in Laminate Materials With a Surface Layer of Copper Film

2005 ◽  
Author(s):  
Akira Matsuba ◽  
Tashiyuki Torii ◽  
DongHui Ma
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Notch Root ◽  
Surface Film ◽  
Fatigue Cracks ◽  
Pure Copper ◽  
Fatigue Crack Initiation ◽  
Copper Film ◽  
Laminate Materials ◽  
Resin Bonding

As model specimens to examine the effects of interlayer resin bonding on fatigue properties in laminate materials with a surface film, pure copper films with a thickness of 100μm and 50μm were bonded with epoxy resin to steel base plates. The fatigue crack propagation from the notch root of the specimen was slower for the epoxy-bonded film than for the base specimen, because the epoxy bonding interlayer restricted crack propagation from the surface film to the inner base plate. On the epoxy-bonded film, however, many fatigue cracks initiated at multiple sites sufficiently away from the notch root, and propagated only on the surface copper film. In addition, the number of these multiple fatigue cracks, caused mostly at the site of the annealing twin boundaries, was larger on the surface copper film with a thickness of 100μm than 50μm.

scholarly journals Performance Evaluation of a Carbon Nanotube Sensor for Fatigue Crack Monitoring of Metal Structures

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4383
Author(s):  
Shafique Ahmed ◽  
Thomas Schumacher ◽  
Erik T. Thostenson ◽  
Jennifer McConnell
Keyword(s):  
Fatigue Crack ◽  
Carbon Nanotube ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Real Time ◽  
False Positive ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Resistance Change ◽  
Metal Structures

This article describes research that investigated the ability of a carbon nanotube (CNT) sensor to detect and monitor fatigue crack initiation and propagation in metal structures. The sensor consists of a nonwoven carrier fabric with a thin film of CNT that is bonded to the surface of a structure using an epoxy adhesive. The carrier fabric enables the sensor to be easily applied over large areas with complex geometries. Furthermore, the distributed nature of the sensor improves the probability of detecting crack initiation and enables monitoring of crack propagation over time. Piezoresistivity of the sensor enables strains to be monitored in real time and the sensor, which is designed to fragment as fatigue cracks propagate, directly measures crack growth through permanent changes in resistance. The following laboratory tests were conducted to evaluate the performance of the sensor: (1) continuous crack propagation monitoring, (2) potential false positive evaluation under near-threshold crack propagation conditions, and (3) crack re-initiation detection at a crack-stop hole, which is a commonly used technique to arrest fatigue cracks. Real-time sensor measurements and post-mortem fractography show that a distinguishable resistance change of the sensor occurs due to fatigue crack propagation that can be quantitatively related to crack length. The sensor does not show false positive responses when the crack does not propagate, which is a drawback of many other fatigue sensors. The sensor is also shown to be remarkably sensitive to detecting crack re-initiation.

Fatigue behavior of an Fe48Cr15Mo14Er2C15B6 amorphous steel

2007 ◽  
Vol 22 (2) ◽  
pp. 544-550 ◽  
Author(s):  
D.C. Qiao ◽  
G.Y. Wang ◽  
P.K. Liaw ◽  
V. Ponnambalam ◽  
S.J. Poon ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Al Alloy ◽  
Test Environment ◽  
Sinusoidal Waveform ◽  
Amorphous Steel

Four-point-bend fatigue experiments were conducted on the Fe48Cr15Mo14Er2C15B6 bulk metallic glass (BMG), amorphous steel, under load control, employing an electrohydraulic machine, at a frequency of 10 Hz (using a sinusoidal waveform) with an R ratio of 0.1, where R = σmin./σmax. (σmin. and σmax. are the applied minimum and maximum stresses, respectively). The test environment was laboratory air. Fe48Cr15Mo14Er2C15B6 exhibited a high fatigue-endurance limit (682 MPa), which is found to be greater than those of the Zr-based BMG, Al-alloy, and high-nitrogen steel. However, the stress versus number of fatigue cycles curve of Fe48Cr15Mo14Er2C15B6 has a significantly brittle fracture mode. Some fatigue cracks initiated from the inclusions or porosities, and the fatigue-crack propagation region was large. However, other cracks initiated from the outer tensile surface of the specimen, and the fatigue-crack propagation region was very small. The mechanisms of fatigue-crack initiation are suggested.

Propagation of Fatigue Cracks in Notched Specimens of EN AW 7475-T761

2013 ◽  
Vol 592-593 ◽  
pp. 789-792 ◽  
Author(s):  
Jürgen Bär ◽  
Gero Wilhelm
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Potential Drop ◽  
Crack Initiation And Propagation ◽  
Notched Specimens ◽  
Initiation And Propagation ◽  
Dc Potential ◽  
Base Load

The influence of single overloads on the fatigue crack initiation and propagation of an EN AW 7475-T761 alloy was investigated using SEN-specimens. Into a base load with an amplitude of 80 MPa and an Rvalue of R=-1 tension compression overloads with an amplitude of 240 MPa have been introduced every 10,000 cycles. The crack length was measured with a DC-Potential drop method. The experiments have shown that cracks are initiated in the first 5% of the total lifetime and, therefore, the cyclic lifetime is dominantly determined by crack propagation. The investigation of the crack surfaces exhibit that a different number of individual cracks propagates within the specimens. The differences in the cyclic lifetimes indicate that the interaction between these cracks directly influences the cyclic lifetime. This shows that the differences in the crack propagation behaviour are responsible for the scatter of the determined cyclic lifetimes.

Multiscale Analysis of Concrete Damage and Crack Propagation Under High Cycle Loading

2019 ◽  
Vol 17 (01) ◽  
pp. 1844007 ◽  
Author(s):  
Xiaoxiao Sun ◽  
Xiaoming Guo ◽  
Li Guo ◽  
Baijian Wu ◽  
Ying Wang
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Finite Size ◽  
Concrete Specimen ◽  
Fatigue Load ◽  
Mesoscopic Structure ◽  
Concrete Damage ◽  
Concurrent Simulation

Concrete is a typical multiphase composite material in which the initiation and propagation of cracks under fatigue load are mainly determined by its mesoscopic structure. In this paper, a concrete multiphase mesoscopic model which considers thickness of interfacial transition zone (ITZ) varying with aggregate’s size is established by the integrated scripting method. The model comprehensively contains the stochastic characteristics of concrete mesoscopic structure. According to the fatigue crack propagation characteristics in different stages, a multiscale method is proposed by establishing the interactive mesoscopic and macroscopic models to targetedly analyze the whole process of fatigue crack initiation, propagation and failure of concrete specimen. Based on the technique of cycle block, concurrent simulation of concrete damage and crack propagation under high-cycle fatigue load is realized. The analysis results show that fatigue cracks in concrete mainly born near the ITZ and gradually enter into the cement mortar matrix to formulate the cracks with finite size. These cracks influence each other until the dominant crack appears and insatiably propagates to result in the failure of specimen.

scholarly journals Crack Propagation in the Tibia Bone within Total Knee Replacement Using the eXtended Finite Element Method

2021 ◽  
Vol 11 (10) ◽  
pp. 4435
Author(s):  
Ho-Quang NGUYEN ◽  
Trieu-Nhat-Thanh NGUYEN ◽  
Thinh-Quy-Duc PHAM ◽  
Van-Dung NGUYEN ◽  
Xuan Van TRAN ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Fracture Prevention ◽  
Patient Specific ◽  
Extended Finite Element ◽  
Tibia Bone ◽  
Age Related ◽  
Final Failure

Understanding of fracture mechanics of the human knee structures within total knee replacement (TKR) allows a better decision support for bone fracture prevention. Numerous studies addressed these complex injuries involving the femur bones but the full macro-crack propagation from crack initiation to final failure and age-related effects on the tibia bone were not extensively studied. The present study aimed to develop a patient-specific model of the human tibia bone and the associated TKR implant, to study fatigue and fracture behaviors under physiological and pathological (i.e., age-related effect) conditions. Computed tomography (CT) data were used to develop a patient-specific computational model of the human tibia bone (cortical and cancellous) and associated implants. First, segmentation and 3D-reconstruction of the geometrical models of the tibia and implant were performed. Then, meshes were generated. The locations of crack initiation were identified using the clinical observation and the fatigue crack initiation model. Then, the propagation of the crack in the bone until final failure was investigated using the eXtended finite element method (X-FEM). Finally, the obtained outcomes were analyzed and evaluated to investigate the age-effects on the crack propagation behaviors of the bone. For fatigue crack initiation analysis, the stress amplitude–life S–N curve witnessed a decrease with increasing age. The maximal stress concentration caused by cyclic loading resulted in the weakening of the tibia bone under TKR. For fatigue crack propagation analysis, regarding simulation with the implant, the stress intensity factorand the energy release rate tended to decrease, as compared to the tibia model without the implant, from 0.152.5 to 0.111.9 (MPa) and from 10240 to 5133 (J), respectively. This led to the drop in crack propagation speed. This study provided, for the first time, a detailed view on the full crack path from crack initiation to final failure of the tibia bone within the TKR implant. The obtained outcomes also suggested that age (i.e., bone strength) also plays an important role in tibia crack and bone fracture. In perspective, patient-specific bone properties and dynamic loadings (e.g., during walking or running) are incorporated to provide objective and quantitative indicators for crack and fracture prevention, during daily activities.

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