New Electrical Potential Method for Measuring Crack Growth in Nonconductive Materials

2003 ◽  
Author(s):  
H. Nayeb-Hashemi ◽  
D. Swet ◽  
A. Vaziri
Keyword(s):  
Thin Layer ◽  
Crack Length ◽  
Crack Growth ◽  
Electric Potential ◽  
Electrical Resistance ◽  
Electrical Potential ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Adhesively Bonded Joint

D.C. electric potential technique has been used to monitor crack growth in conductive materials. A constant DC current is ppased through thesse materials and the crack length is measured through the changes in the electrical voltage at the crack mouth. However, this method is not applicable in crack growth measurement in nonconductive materials or adhesively bonded joints. For these materials, a new method is developed and is shown to provide a very accurate method for measuring the crack length. The surface of these materials is coated with a thin layer of carbon paint and the crack lenght is measured through the changes in the electrical resistance of the carbon paint, as the crack grows both in the base material and the thin layer carbon paint. In contrast to the D.C. electric potential technique where the position of the probes for measuring the crack length is very important for an accurate measurement of the crack length, the new technique is little sensitive to the probe location. Crack growth is measured in adhesively bonded joints subjected to creep loadings. A modified Compact tension specimen is cut in two pieces across its notch area. The pieces are then glued jusing an adhensive. The surface of the specimen is painted with a thin layer of carbon paint and the changes in its electrical resistance are monitored. It is shown that the carbon paint method provides a quiet sensitive method for monitoring the crack growth. The creep crack growth rate in the adhesively bonded joint is related to Mode I energy release rate, G1. It is shown that the crack grows in the middle of the adhesive layer rather than at the interface of the joint. Micromechanisms of the crack growth are studied using a scanning electron microscope. The damage consists of numerous crazed regions at the crack tip. Crack grows by the linkage of the crazed region.

scholarly journals Development of an integrated sacrificial sensor for damage detection and monitoring in composite materials and adhesively bonded joints

2021 ◽  
pp. 147592172198904
Author(s):  
G Ólafsson ◽  
RC Tighe ◽  
SW Boyd ◽  
JM Dulieu-Barton
Keyword(s):  
Crack Initiation ◽  
Electrical Resistance ◽  
Electrical Response ◽  
Lap Joints ◽  
Structural Performance ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Wide Range ◽  
Adhesively Bonded Joint

Quality assurance of adhesively bonded joints is of vital importance if their benefits are to be exploited across a wide range of industrial applications. A novel lightweight, low-cost, non-invasive embedded sacrificial sensor is proposed, capable of detecting damage within an adhesively bonded joint, which could also be used in a laminated composite structure. The sensor operation uses changes in electrical resistance, increasing as the sensing material area diminishes with damage progression. Initial tests prove the sensor concept by showing that the electrical resistance of the sensor increases proportionally with material removal, mimicking the sensor operation. Thermography is used to verify the current flow through the sensor and that any localised heating caused by the sensor is minimal. Short beam interlaminar shear strength (ILSS) tests show that embedding sensors in a composite laminates did not cause a reduction in material interfacial structural performance. Finally, the in situ performance of the sensor is demonstrated in quasi-static tensile tests to failure of adhesively bonded single lap joints (SLJs) with sensors embedded in the bond line. Prior to crack initiation, an electrical response occurs that correlates with increasing applied load, suggesting scope for secondary uses of the sensor for load monitoring and cycle counting. Crack initiation is accompanied by a rapid increase in electrical resistance, providing an indication of failure ahead of crack propagation and an opportunity for timely repair. As the crack damage propagated, the electrical response of the sensor increased proportionally. The effect of the sensor on the overall structural performance was assessed by comparing the failure load of joints with and without the embedded sensor with no measurable difference in ultimate strength. The research presented in the article serves as an important first step in developing a simple yet promising new technology for structural health monitoring with numerous potential applications.

Effect of Temperature on Shear Strength of Adhesively Bonded Joints for Automobile Industry

2011 ◽  
Vol 418-420 ◽  
pp. 1259-1265 ◽  
Author(s):  
Ping Hu ◽  
Xiao Han ◽  
Long Li ◽  
Qi Shao ◽  
Wei Dong Li
Keyword(s):  
Shear Strength ◽  
Automobile Industry ◽  
Driving Safety ◽  
Effect Of Temperature ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Joint Shear Strength ◽  
Adhesively Bonded Joints ◽  
Fracture Surfaces ◽  
Adhesively Bonded Joint

Due to the significant effect on vehicle lightweight, adhesively bonded joint in structural components is widely adopted in automobile industry in recent years, which leads to the benefits in fuel economy, reduced emissions and driving safety. In this paper, the performances of adhesively bonded joints with three different adhesive types after different temperature treatments are investigated through joint shear strength test. Visual inspection is performed on fracture surfaces after joint failure. Results showed that both low and high temperatures have impact on joint strength and lead to different fracture modes. Stiff and flexible adhesives also result in different fracture surfaces in the overlap zone as the temperature varies.

scholarly journals Impact Fatigue of Adhesive Joints

2008 ◽  
Vol 399 ◽  
pp. 71-78 ◽  
Author(s):  
Vadim V. Silberschmidt ◽  
Juan Pablo Casas-Rodriguez ◽  
Ian A. Ashcroft
Keyword(s):  
Crack Growth ◽  
Growth Process ◽  
Bonded Joints ◽  
Impact Fatigue ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Tensile Fatigue ◽  
Damage Processes ◽  
Microstructural Studies ◽  
Loading Type

The paper presents results of studies into the effect of repetitive low-energy impacting (known as impact fatigue) on reliability and crack growth in adhesively bonded joints. This type of loading is compared to the standard tensile fatigue in order to assess severity of such loading regime. Another loading type studied is a combination of a small portion of repetitive impacts with tensile fatigue. Crack propagation in a joint exposed to these types of loading is studied experimentally and numerically (with finite elements). This analysis is accompanied by microstructural studies of various damage processes, active at different stages of the crack growth process.

Studying Effects of Arc Discharge Surface Texturing on Stress Distribution in Adhesively Bonded Joints by Using Finite Element Modeling

2011 ◽  
Author(s):  
Mehdi Asgharifar ◽  
Fanrong Kong ◽  
Blair Carlson ◽  
Radovan Kovacevic
Keyword(s):  
Stress Distribution ◽  
Adhesive Bonding ◽  
Arc Discharge ◽  
Treatment Method ◽  
Bonded Joints ◽  
Textured Surfaces ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints ◽  
Optical Profilometer ◽  
Adhesively Bonded Joint

This study investigates the potentiality of using atmospheric-pressure Direct Current (DC) plasma arc discharge as a surface treatment method of aluminum alloys in adhesively bonded joints in order to enhance adhesion. The surface morphology exposed to the arc for the current of 40 A (low intensity) and the plasma torch scanning speeds between 20 and 120 mm/s, exhibits a micro-scale surface roughness appropriate for adhesive bonding. The arc textured surfaces are characterized by using an optical profilometer. Additionally, the effect of modified surface on the stress distribution throughout the single-lap adhesively bonded joint in tension is explored by 2D FEM. The geometrical model for FE analysis of adhesively bonded structure is generated by including the surface texture coordinates obtained from the optical profilometer.

Crack growth in adhesively bonded joints subjected to variable frequency fatigue loading

2003 ◽  
Vol 79 (12) ◽  
pp. 1161-1182 ◽  
Author(s):  
A. H. Al-Ghamdi ◽  
I. A. Ashcroft ◽  
A. D. Crocombe ◽  
M. M. Abdel-Wahab
Keyword(s):  
Crack Growth ◽  
Fatigue Loading ◽  
Variable Frequency ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints

Experimental Characterization of Crack Growth Behavior in Adhesive Interface under Impact Loading

2016 ◽  
Vol 715 ◽  
pp. 116-121 ◽  
Author(s):  
Sota Oshima ◽  
Hisayoshi Ishida ◽  
Ryota Tanegashima ◽  
Takayuki Kusaka ◽  
Tomo Takeda
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Growth Behavior ◽  
Image Correlation ◽  
Crack Growth Behavior ◽  
Bonded Joints ◽  
Adhesively Bonded ◽  
Adhesively Bonded Joints

A novel experimental method has been developed to evaluate the mode I crack growth behavior of adhesively bonded joints under impact loading. The split Hopkinson pressure bar (SHPB) technique and the digital image correlation (DIC) technique was employed to evaluate the crack growth behavior. To reduce the dynamic effects by controlling loading input of the SHPB apparatus, the fracture toughness was determined precisely based on static evaluation formula. To contrive the testing set-up, high loading rate was kept until the arrest of crack. The fracture toughness of titanium alloy/epoxy adhesively bonded joints during crack propagation was obtained successfully by using present method.

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