Decibel NDE Inspections & Training Institute

Plate lamination defect is one of the primary processing discontinuity that originates during hot or cold forming processes and is considered as a serious metal plate defect.  All the metals contain discontinuities at micro and macro levels. These discontinuities, when above the acceptance level, are termed as defects. The discontinuities in metal are classified according to the stage of manufacturing in which they initiate.  Plate lamination defect can be defined as flat and thin subsurface separations present inside metal plate, parallel to the surface of the plates. The sources of this defect are inherent discontinuities present in metal such as inclusion and porosity, which are flattened during the rolling process.  Carbon Steel Plate Lamination Defect & Reasons A carbon steel plate is produced by the process of hot or cold rolling a thick slab. During this process, carbon steel may pass through the rollers many times to achieve the desired thickness. Each p...

Square wave is a shape of the signal In the UT instruments the shape of firing pulse may be either spike or unipolar square wave or bipolar square wave; for the square wave firing pulse the half wave duration is tunable whilst the rising and falling edges should be kept as short as possible; also the stability of the amplitude should be provided within entire half wave duration. The video below shows the 3 types of firing pulse noted above - at the time of capturing of the video the standard load of 50 Ohm was connected to the pulser terminal, not the probe https://www.youtube.com/watch?v=8HPKQ9gXooo&spfreload=10 Upon the probe is connected the efficiency of the spike / unipolar and bipolar square wave may be understood based on the observation of the echo returned from the material - this is illustrated by the video below https://www.youtube.com/watch?v=wyTTCLMNqXQ The half wave duration around 1/(2F) in the firing pulse (pulse Width) provides the maximal efficiency (F is the...

Comparison of the use of rutile and cellulosic electrodes Types of electrodes and their compositions Many types of manual metal arc (MMA) electrodes are available on the market. Depending on the main constituent of their flux, they are grouped into three categories: cellulosic, rutile and basic. All electrodes consist of a cored wire (typically 2.5–6mm diameter) coated by a flux. The core wire is generally made of low-quality riming steel and the fluxes contain many elements allowing refinement of the weld macrostructure. The composition of the flux impacts the electrodes’ behaviour. The main constituents of the different types of electrodes and the shielding gas created for each are described in Table 1 (Bowniszewski, 1979). Table 1 Main constituent of the three possible types of electrodes and shielding gas created by its combustion. Electrode type Main constituent Shielding gas created Rutile Titania (TiO2) Mainly CO2 Basic Calcium compounds Mainly CO2 Cellulosic ...