Papers by Keyword: Defect

Abstract: Wafer scratching from handling and processing can impact the performance of devices grown on a substrate. Knowledge of process conditions and modeling of scratches on wafers can be used to elucidate the root cause of scratches so that they can be eliminated.

Abstract: In this paper presents the computer simulation results on the investigations of the ion scattering processe on the defect InP(001)<110>,<ī10> surface under low-energy grazing ion bombardment have been presented. The peculiarities trajectories of the scattered ions from surface defect, atomic chain and semichannel have been investigated by computer simulation. It was found some trajectories nearby surface atomic chain which have loop shape and a line form. At grazing ion incidence, from a correlation of the experimental and calculated energy distributions of the scattered particles, one may determine a spatial extension of the missing atom on the monocrystal surface damaged by the ion bombardment.

Abstract: The article discusses the types of dangerous defects in welded joints. The main methods of non-destructive testing are described, their advantages and disadvantages are briefly reflected. The comparison of the automated ultrasonic testing methods with radiographic ones is given on the example of testing the welded joints of ASME DN350 Py250 pipe fittings with a thickness of the welded edges of 53.9 ÷ 61.3 mm. The comparison results of the methods by the criterion of the accuracy of determining the coordinates of defects are presented, which show the expediency of replacing the automated ultrasonic method with the radiographic one, provided that the thickness of the welded edges is shallow.

Abstract: The article presents a method for eliminating the crystallization of thermal nodes and shrinkage defects in the form of micro-friable cavities. The method of soldering on castings from steel grades VNL-1 and VNL-6 using 5VA powder solder has been investigated. Also, the optimal soldering modes were determined, the effects of soldering modes on the properties of the base material and the soldered joint were studied, the corrosion resistance was investigated, the corrosion resistance of the soldered joints in corrosive environments. The conducted studies of sealing by soldering cast parts with microdefects lead to the following results: increased corrosion resistance; ensuring increased tightness; improving the presentation; elimination of surface microdefects.

Abstract: Effects of Mn-substitution on magnetic properties of Zn_1-xMn_xO (MZO) nanoparticles with x= 0.00, 0.03, 0.05 and 0.07 have been investigated along with their local structure. Study on Mn K-edge XANES spectra of MZO reveals that the oxidation state increases by Mn-substitution, which further implies that MZO exhibits a mixed valence state of Mn³⁺/Mn⁴⁺. The local structure analysis on Mn K-edge EXAFS spectra shows that the coordination number (CN) of Mn reduces by increasing Mn concentration, thus the amount of oxygen vacancy (V_O) increases by Mn-substitution. Interestingly, the magnetization of MZO also tend to increase as the Mn concentration increases. The M(H) curves exhibit a linear (paramagnetic) behavior, showing no evidence of room-temperature ferromagnetism. Our results show that magnetism of MZO is related to the correlation between Mn magnetic moment and V_O.

Abstract: This experiment is to investigate delamination damage of carbon/basalt/epoxy hybrid composites on the drilling manufacturing process. The damage is caused by drilling on wet and dry conditions with a twist drill size of 8 [mm], and 10 [mm] have been conducted. This experiment was carried out based on the ASTMD 5470-12 standard. Three hybrid composites have been manufactured for samples such as H₁, H₂, and H₃. Additionally, the carbon fibers reinforced epoxy composites (CFRP) and basalt fibers reinforced epoxy composites (BFRP) as experiment control had built. The aim is to assess the defect zone of carbon/basalt hybrid composite against the drilling. The examination results showed that the feed rate speed of various laminate configurations e.g., H₁, H₂, and H₃, on drilling dried between twist drill of 10 [mm] and 8 [mm] diameters are 50.5 %, 25 %, and 33.2 %, respectively. Also, adding lubricant during the drilling work has reduced peel-out and push-out effectively. The delamination defect has been the high resulted in drilling using drill 10 [mm] in wet or dry conditions. In contrast, delamination defect has occurred minimum on drilling hole using twist drill 8mm in work wet and dry condition. It has still occurred. From this research, the combination sequence of basalt and carbon fiber has the possibility to experience the delaminate damage in dry drilling processes.

Abstract: Sand casting is one of manufacturing process that still exist today. Numerous products are produced to serve industrial and domestic use. Defect could lead to product performance, and unfortunately inevitable in a casting process. This paper aim to investigate typical defect resulted from sand casting process. An aluminum cooling fan was selected as the model since it has complicated shape with different thicknesses. The casted fan was investigated under photo micro for defect analysis. Porosity, gas inclusion, pinhole, and shrinkage were found as the common defects occured at different part of the fan.

Abstract: Microstructure of ingot and industrial blanks made of copper M2 was examined for quality control. Microstructure was examined by means of traditional metallographic analysis methods. Exogenous nonmetal inclusions and pores in microstructure were found. The transition from exogenous inclusions and pores, which were not removed in initial processing stage, to the crack, which leads to billet destruction on one of last processing stages, is shown. Without quality control of copper blanks by a metallographic method, it is impossible to provide guarantee of reliable operation of machines and responsible purpose constructions. A comparative study of the temperature dependences of the viscosity of the melts of charge materials and finished ingots for copper M2 was carried out. The study of the viscosity of copper melts M2 was carried out with the aim of quality control in the chain of "charge-melt-ingot" at the foundry stage.

Abstract: The article discusses the manufacturing technology of the impeller of a high-pressure centrifugal fan using high-speed direct laser spraying. The outer diameter of the part is 1200 mm, the total weight is 100 kg. The material used is metal powder stainless steel 316L. Features of the manufactured products were researched, including possible thermal deformations and methods for dealing with them.

Abstract: In this paper, a complex study of composite materials of different nature for the presence of internal defects after the application of impact damage was carried out. The dependence of the initiation energy on material damage from the magnitude of the impact energy is obtained. The areas of sample bundles were investigated by ultrasonic testing (UT). The structure of samples from composite materials was monitored using an industrial microtomography system. A technique was developed that allows highly accurate determining the size of internal sample defects by means of computed tomography (CT).