Лако-красочные материалы — производство

As with any other technical component or material, the most frequently asked question about adhesive bonds concerns its strength, defined as the maximum stress or strain under which the bond will fail or be destroyed. The ultimate tensile strength of adhesive joints is determined almost exclusively in tensile shear tests using single­lap shear specimens that […]

The engineer describes the mechanical behavior of materials and components by means of quantitative parameters that can be determined by measurement under defined conditions, such as strength, deformability and weight. In the case of adhesive bonds, it is advisable to distinguish between the mechanical behavior as a function oftime and temperature on the one hand, […]

The establishment of special requirements for the nondestructive testing of bonded assemblies helps to define suitable criteria for nondestructive testing methods in general. These refer to the applicability of a specific method for the nondestructive testing of bonded joints, the test equipment required, the time needed to test the component, the safety at work, the […]

In active thermography, a proper energy source must supply or transfer sufficient energy to the sample to generate an adequate temperature contrast, and this is the first objective of these testing methods. The amount of energy must also be capable of generating a contrast, without damaging the component [6]. Pulse thermography and lockin thermography use […]

Ultrasound burst phase thermography is a new nondestructive defect-selective technique originating from ultrasonic lockin thermography. It provides thermal wave images of defects by ultrasonic stimulation. In contrast to the sinusoidal-modulated excitation used by lockin thermography, conventional pulse thermography is based upon short optical or acoustical excitation Figure 7.23 The transformation of vibration energy into heat […]

7.6.5.1 Optical and Ultrasonic Lockin Thermography In optical lockin thermography (OLT), a thermal wave is produced on the entire surface of a sample by periodic irradiation with a infrared heat source, the intensity of which can be modulated (see Figure 7.20). For each picture element, a thermographic camera records the thermal response of the surface […]

In this method an ultrasound pulse is propagated through the entire structure and received by a second probe, making it possible to evaluate the adhesive joint and to detect delaminations in glass-fiber reinforced plastics. The amplitude of the signal received is compared to a reference value, for example the amplitude of the initial signal. The […]

The pulse echo technique is the simplest method for detecting defects in an adhesive joint. The sample is placed into a water bath, as is the probe that supplies ultrasound to the sample; the system is shown schematically in Figure 7.19. The amplitude of the measured signal allows conclusions to be drawn with regard to […]

7.6.4.1 Impulse-Induced Resonance This technique was developed to test assemblies made from sheet metals and nonmetallic backing elements. Pulses that are created by broadband ultrasonic transducers and long enough to produce stationary waves are transferred to the metal sheet via an appropriate medium. The metal sheet has a thickness resonance spectrum of frequencies within the […]

Magnetic, electrical or chemical techniques are not well suited to the nondestructive testing of adhesive joints, due to the fact that the adhesive layer acts as an insulator when these techniques are used. Consequently, the measurement of capacitance or induction for the testing of adhesive joints is used only to a limited extent. It is […]