Analysis of the causes of control panel inconsistencies in the gravitational casting process by means of quality management instruments

All castings can have defects caused by, for example, deviations in material characteristics, structure or properties, but the skillful use of available technologies and quality management tools allows for the detection and elimination of casting incompatibilities as well as the prevention of their recurrence in the future. The aim of the article was to analyse the types of defects in castings, locate the areas with the most frequent occurrence of defects and identify the reasons for the presence of defects in castings of the control panel and its cover. The paper presents the usefulness of a combination of quality management instruments for diagnosing material discontinuities in the analyzed castings.

Damage imaging in a stiffened curved composite sandwich panel with wavenumber index via Riesz transform

Imaging a damage using the phase of wavefield “video” in the physical domain is developed and applied to a stiffened curved composite sandwich panel for visualization of a barely visible impact damage. The ultrasonic guided waves are generated by the thermoelastic effect induced by a Nd:YAG Q-switched pulse laser and then are captured point-by-point by a laser Doppler vibrometer. The wavefield “video” is reconstructed by measuring out-of-plane velocity on the smooth outside surface of the panel. Newly generated wavenumbers from the geometry/material discontinuities caused by either the stiffener or the impact damage can be detected by observing the change of wavenumber from the reconstructed wavefield “video.” The instantaneous wavenumber (i.e. the magnitude of instantaneous wavevector) derived via Riesz transform and its difference can be shown and highlighted using a proposed imaging condition, named as wavenumber index. The wavenumber index sums the wavenumber values followed by a wave energy threshold filter which is performed in the time domain. This is in contrast to other imaging conditions implemented in the frequency-wavenumber domain by the use of complex wavenumber filtering and wave mode decomposition. Since wavenumber index is the phase-based imaging technique instead of conventional intensity-based technique for the wavefield “video,” this technique is robust in that the impact damages located in the vicinity of geometry/material discontinuities can yield consistent damage image resolution with high sensitivity even for wave propagating from the direction across the stiffener. The barely visible impact damage of the composite structure becomes therefore “visible” with the proposed imaging technique.

Bending and Springback Analysis on Sheet Metal Material Discontinuity

Origami concept came up as an emerging technique for sheet metal bending or folding and is called as Origami-based sheet metal (OSM) folding. This process fits right in criteria of effectiveness, efficiency, and sustainable manufacturing due to minimal resources required to make the fold or bend. In this process, the line was created on which the bend was supposed to perform. Traditionally the intermittent material was removed from that line with a through cut. Then the bend was performed. During bending the force required was very less and thus it can also be called as easy bend operation. Because the material and removed all the way through the thickness of the metal, these part after bending cannot be used to contain particles smaller than the cut width or liquid solution due to leakage issue. To overcome this issue, this paper investigates the material discontinuities with a blind cut, where the material through the thickness was not completely removed. For this 4 sample types were created. Three additional variables were added in placing the sample during bend operation. Experiments were performed and bending deformation and springback were analyzed. After analyzing the results, it was found that significant thickness difference regions in the sample, smaller clearance, smaller width or cut, and width of cut facing punch are the best variable to have a better bending and less springback.

Trustworthiness in Modeling Unreinforced and Reinforced T-Joints with Finite Elements

As required by regulations, Finite Element Analyses (FEA) can be used to investigate the behavior of joints which might be complex to design due to the presence of geometrical and material discontinuities. The static behavior of such problems is mesh dependent, thus these results must be calibrated by using laboratory tests or reference data. Once the Finite Element (FE) model is correctly setup, the same settings can be used to study joints for which no reference is available. The present work analyzes the static strength of reinforced T-joints and sheds light on the following aspects: shell elements are a valid alternative to solid modeling; the best combination of element type and mesh density for several configurations is shown; the ultimate static strength of joints can be predicted, as well as when mechanical properties are roughly introduced for some FE topologies. The increase in strength of 12 unreinforced and reinforced (with collar or doubler plate) T-joints subjected to axial brace loading is studied. The present studies are compared with the literature and practical remarks are given in the conclusion section.

Active thermography as a tool for internal composite structure observation and evaluation

Purpose The purpose of this paper is to study if it is possible applying infrared thermography (both vibro and pulsed) to detect and localise material discontinuities as well as to find the place where the inclusion was introduced. Design/methodology/approach The experimental investigation is performed on samples manufactured during infusion process. The measurements were performed on three four-layered rectangular composite samples with discontinuities. The discontinuities introduced in the samples were as follow: all three samples between first and second layer counting form the bottom two optical fibres (OFs) were embedded and additionally: sample no. 1 – one of the OF was broken, sample no. 2 – the drop of water was introduced, and sample no. 3 – the little amount of dust was introduced. Findings For some discontinuities, the vibrothermography is excellent tool (placement of broken OF, drop of water), for same is not sufficient (healthy OFs or dust). For dust, the pulsed thermography seems to be the required tool. Different approaches (vibrothermography and pulsed thermography) for the same sample will confirm that for same defects vibrothermograpy is better and for some pulsed thermography – complex combination of different thermography approaches is needed to have complex response about sample structural condition. Originality/value The presented paper is an original research work. There are very limited literature papers applying both vibro and pulsed thermography for one problem. The assessment of different discontinuities (inclusions) and detailed analysis is presented.