Automated Ultrasonic Inspection of Adhesive Joints and Three-Layer Structures Made of Polymer Composite Materials

NDT World ◽  
2021 ◽  
pp. 36-40
Author(s):  
Vladimir Ivanov ◽  
Gennady Starikovsky ◽  
Andrey Boitsov ◽  
Anastasiya Zagumennova ◽  
Nikolay Kruchinkin ◽  
...  
Keyword(s):  
Polymer Composite ◽  
Ultrasonic Testing ◽  
Adhesive Joints ◽  
Ultrasonic Technique ◽  
Honeycomb Core ◽  
Air Inlet ◽  
Layer Structures ◽  
Ultrasonic Techniques ◽  
Core Height ◽  
Detection Of Defects

Introduction. The research considers the NDT results with through-transmission ultrasonic techniques of samples of adhesive joints and three-layer polymer composite structures with artificial defects simulating the common failures of parts for aerospace equipment. The purpose of the conducted research was to determine the detectability of common defects in such structures during an automated ultrasonic testing. A set of samples prepared for the research had artificially embedded defects, simulating the delamination of skins and disbonds of adhesive joints. The set consisted of four types of samples with different skin material; with different material, height and size of honeycomb cells (for three-layer structures) and with different types of adhesive joints — for reinforced stringer structures. Method. These samples were analyzed using two types of automated through-transmission ultrasonic techniques. The first type is transmission of ultrasound through a layer of air, the second type is through a jet of water. Two automated systems were used:, a Technische Beratung Schittko GmbH machine for the first case, and Tecnatom robotic system for the second case. Pseudocolor C-scan is a diagnostic testing document for both systems. C-scan analysis is based on the thresholding method. Results 1. The inspection of stringer samples demonstrated that they can be inspected with a non-contact technique using an air inlet at frequencies of 40 and 500 kHz with a sensitivity of at least 1 cm2. The water jet inspection of adhesive joints at frequencies of 1 MHz and 5 MHz can provide a sensitivity of 0.3 cm2. 2. All samples of three-layer structures, including honeycomb cores of various thicknesses, turned out to be uninspectable when tested with an air inlet at a frequency of 500 kHz. 3. Three-layer structures with a honeycomb core height of up to 8 mm can be inspected with the non-contact through-transmission ultrasonic technique at a frequency of 40 KHz with a sensitivity of 5 cm2. Such structures can also be inspected with the jet method at a frequency of 1 MHz with a sensitivity of 1 cm2. 4. Three-layer structures with a honeycomb core height of 80 mm and more cannot be inspected with the through-transmission ultrasonic technique using an air inlet due to the significant ultrasonic attenuation. They can be inspected with the jet method at a frequency of 1 MHz with a sensitivity of 1.8 cm2. Conclusion. Automated through-transmission ultrasonic testing of three-layer structures and adhesive joints ensures reliable detection of defects with a diameter of 15 mm for adhesive joints of monolithic parts and detection of defects with a diameter of 15–25 mm for three-layer structures, depending on the thickness of the skin and core.

scholarly journals Early Detection of Defects through the Identification of Distortion Characteristics in Ultrasonic Responses

Mathematics ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 850
Author(s):  
Pietro Burrascano ◽  
Matteo Ciuffetti
Keyword(s):  
Early Detection ◽  
Additive Noise ◽  
Linear Models ◽  
High Stress ◽  
Damage Index ◽  
Hammerstein Model ◽  
Linear Behavior ◽  
Non Linear ◽  
Ultrasonic Techniques ◽  
Detection Of Defects

Ultrasonic techniques are widely used for the detection of defects in solid structures. They are mainly based on estimating the impulse response of the system and most often refer to linear models. High-stress conditions of the structures may reveal non-linear aspects of their behavior caused by even small defects due to ageing or previous severe loading: consequently, models suitable to identify the existence of a non-linear input-output characteristic of the system allow to improve the sensitivity of the detection procedure, making it possible to observe the onset of fatigue-induced cracks and/or defects by highlighting the early stages of their formation. This paper starts from an analysis of the characteristics of a damage index that has proved effective for the early detection of defects based on their non-linear behavior: it is based on the Hammerstein model of the non-linear physical system. The availability of this mathematical model makes it possible to derive from it a number of different global parameters, all of which are suitable for highlighting the onset of defects in the structure under examination, but whose characteristics can be very different from each other. In this work, an original damage index based on the same Hammerstein model is proposed. We report the results of several experiments showing that our proposed damage index has a much higher sensitivity even for small defects. Moreover, extensive tests conducted in the presence of different levels of additive noise show that the new proposed estimator adds to this sensitivity feature a better estimation stability in the presence of additive noise.

Effects of Cure State on the Ultrasonic Nonlinear Parameter in Adhesive Joints

2000 ◽  
Author(s):  
Guoli Liu ◽  
Jianmin Qu ◽  
Laurence J. Jacobs
Keyword(s):  
Narrow Band ◽  
Harmonic Signal ◽  
Adhesive Joints ◽  
Nonlinear Parameter ◽  
Curing Temperature ◽  
Curing Time ◽  
Curing Conditions ◽  
Polymer Adhesive ◽  
Ultrasonic Techniques ◽  
Transmitted Signal

Abstract The objective of this paper is to characterize the cure state of polymer adhesive joints using nonlinear ultrasonic techniques. To this end, through transmission tests were carried out on joint samples that had been subjected to various curing conditions. In these tests, a 40-cycle harmonic signal was generated by a 2MHz narrow-band PZT transducer as the incident wave. The wave transmitted through the adhesive joint was received with a 4MHz narrow-band PZT transducer. The magnitude of the second order harmonics in the transmitted signal was measured and the corresponding nonlinear parameter β was calculated. A fairly good correlation was observed between the nonlinear parameter and the cure state. It was found that under-curing (lower curing temperature or short curing time) tends to increase the nonlinear parameter.

Research on Phased Array Ultrasonic Technique for Testing Tube to Tube-Sheet Welds of Heat Exchanger

2016 ◽  
Author(s):  
Weican Guo ◽  
Shengjie Qian ◽  
Zhangwei Ling ◽  
Dongsheng Hou
Keyword(s):  
Heat Exchanger ◽  
Ultrasonic Testing ◽  
Phased Array ◽  
Incomplete Fusion ◽  
Testing System ◽  
Ultrasonic Frequency ◽  
Ultrasonic Technique ◽  
Tube Sheet ◽  
Element Size ◽  
Array Probe

The tube to tube-sheet weld is the main connection structure of heat exchanger. This paper presents the phased array ultrasonic technique for testing the tube to tube-sheet welds of heat exchanger. The optimization analysis of phased array parameters and the simulation on the acoustic field with CIVA software were completed. The mentioned phased array parameters included array elements, array element size, deflection angle, ultrasonic frequency and so on. An ultrasonic testing system was designed and fabricated in accordance with the structure of heat exchange tube and fillet welds position. The ultrasonic C-scan was carried out by the ultrasonic testing system with its circumferential scanning by a mechanical scanning device while the axial electronic linear scanning by the phased array probe. At last, tests on samples with the porosity and incomplete fusion flaws were performed by the ultrasonic testing system. Experimental results showed that the phased array ultrasonic technique could effectively detect the porosity flaws and the incomplete fusion flaws in the tube to tube-sheet welds of heat exchanger.

Vibration Characteristics of Hybrid Honeycomb Core Sandwich Structure with FG-CNT Reinforced Polymer Composite Faces under Various Thermal Fields

2021 ◽  
Vol 21 (11) ◽  
Author(s):  
S. Swetha ◽  
P. Thamilselvi ◽  
Vinod Bhagat ◽  
M. P. Arunkumar
Keyword(s):  
Polymer Composite ◽  
Forced Vibration ◽  
Sandwich Structure ◽  
Thermal Environment ◽  
Vibration Characteristics ◽  
Temperature Fields ◽  
Honeycomb Core ◽  
Reinforced Polymer ◽  
Nonlinear Temperature ◽  
Composite Face

This paper presents the free and forced vibration characteristics of a hybrid honeycomb core sandwich structure consisting of a top and bottom FG-CNT reinforced polymer composite face sheet in a thermal environment. Different thermal fields like the uniform, linear and nonlinear temperature fields in the thermal environment along the thickness direction are considered to study the dynamic characteristics of the hybrid honeycomb core sandwich structure. The mathematical model is developed using Hamilton’s principle along with the third-order shear deformation theory. Five unknown modal coefficients are found using the modal superposition principle to calculate the forced vibration response. From the free and forced vibration results, it is observed that the FG-V[Formula: see text] grading pattern face sheets with lower cell size honeycomb core and with higher cell wall thickness honeycomb core show better vibration characteristics. It is noticed that the sandwich structure with honeycomb core and FG-V[Formula: see text] CNT reinforced polymer composite face has a higher critical buckling temperature in the thermal environment. Furthermore, for different percentages of critical buckling temperature, the natural frequencies and vibrating patterns for uniform, linear and nonlinear temperature fields are the same for the sandwich structure with UD, FG-V[Formula: see text] and FG-[Formula: see text]V CNT reinforced polymer composite faces. In addition, the resonant peak of the sandwich structure with FG-V[Formula: see text] CNT reinforced polymer composite face in nonlinear temperature field shifts more toward the right, while that of the uniform temperature field shifts more toward the left in the velocity response.

ALKALI ACTIVATED FLY ASH BASED CONCRETE: EVALUATION OF CURING PROCESS USING NON-LINEAR ULTRASONIC APPROACH

2021 ◽  
pp. 1-26
Author(s):  
Arash Nikvar-Hassani ◽  
Hamad N. Alnuaimi ◽  
Umar Amjad ◽  
Saptarshi Sasmal ◽  
Lianyang Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Unconfined Compressive Strength ◽  
Curing Process ◽  
Ultrasonic Technique ◽  
Ultrasonic Signals ◽  
Non Linear ◽  
Ultrasonic Techniques ◽  
Alkali Activated ◽  
Testing And Evaluation

Abstract This paper investigates the applicability of nondestructive testing and evaluation (NDT&E) method using ultrasonic signals to monitor the curing of alkali activated fly ash based concrete (AAFC). The evaluation was carried out on AAFC specimens with two different water/binder (W/B) ratios of 0.3 and 0.5 and after curing at 60 °C for 7, 14 and 28 days, respectively. The signals are recorded and analyzed using linear and non-linear ultrasonic techniques. The results show that the non-linear ultrasonic technique has a clear advantage over the linear ultrasonic technique when monitoring the curing of AAFC specimens with the lower W/B ratio. However, the specimens with the higher W/B ratio do not undergo proper curing and therefore do not show clear distinctions between the curing times measured from the two ultrasonic techniques. The unconfined compressive strength (UCS) of the AAFC specimens at different W/B ratios and curing times is also measured. The UCS results showed a good correlation with the ultrasonic results.

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