Papers by Keyword: Thinning

Abstract: Bipolar plates are key components of fuel cell systems, as they significantly determine efficiency, power density, and service life. In aerospace applications, their importance is further emphasized due to the dual requirement of corrosion resistance and strict weight reduction. Titanium Grade 1 combines low density and excellent corrosion resistance. However, its industrial application is limited by restricted formability. The aim of this paper is a systematic investigation of the forming behavior of Titanium Grade 1 foil material in order to define forming limits and derive manufacturing-oriented design recommendations for bipolar plates in aviation. Procedure. Sixteen distinct geometry features were developed to represent characteristic forming conditions. In addition to cross-section variations, the flow field angle was systematically altered to assess its influence on local stress and strain distribution. Furthermore, the key process parameters forming speed, forming force, and lubricant amount were varied to evaluate their impact on the forming quality. The assessment focused on form filling and material thinning. For this purpose, metallographic cross-sections were prepared, and optical 3D measurements were conducted using a Keyence system to precisely capture local wall thickness variations. Key findings Process parameters: The forming behavior of Titanium Grade 1 is strongly influenced by the applied forming force and lubrication. Form filling becomes sufficient only above 350 MPa (3.000 kN), while the lubricant amount is decisive for achievable forming depths due to the hydrostatic oil cushion effect. In contrast, forming speed shows no significant influence. Anisotropy remains a critical factor, particularly in 0° rolling direction, where premature thinning leads to fracture. Geometry parameters: Small radii are highly critical, while feature depth leads to expectedly higher thinning. Steeper flank angles improve form filling but at the cost of increased thinning. Pitch shows limited influence, although it may become relevant at very small values. Channel design is challenging, as sharp flow field angles consistently result in severe thinning and pose difficulties in tool manufacturing.

Abstract: Single point incremental forming (SPIF) is a part of the branch of incremental sheet metal forming (ISF) processes. This alternative has demonstrated several outcomes, including low produc tion cost, flexibility, and capability to manufacture various intricate sheet metal parts in automotive, aerospace, medical applications, etc. In the present investigation, the SPIF process performed to ex amine the influence of the process parameters, including the step depth and the feed rate, on the wall thickness distribution of the deformed shape. Results indicate that the step depth has the predominant impact on the reduction of wall thickness.

Abstract: During forming the process, various geometric parameters play an important role in determining the amount of the springback. These parameters can include factors such as sheet thickness, friction coefficient, and the radii of the dies. Furthermore, it is important to note that this phenomenon is also influenced by the material selection and the applied load. However, this research aims to investigate the impact of radii of both lower and upper dies, as well as the blank holder force on the springback amount, and the thinning percentage that occurs during elastic recovery of the material during the deep drawing process. The investigation will be followed by the development of an optimization strategy.

Abstract: Deep drawing process is a common sheet metal forming technique in motor vehicle manufacturing. There are three primary defects that could be occur in deep-drawn parts: tearing, wrinkling, and thinning. When the thinning is difficulty detected by visual inspection. As a result, this study aims to address the thinning issue in a fuel tank part made from an aluminum alloy sheet AA5754-O 1.5 mm thick under cold working deep drawing process, while the manufacturer's desired upper limit for thinning is 20%. Two influential parameters viz. blank holder force and initial size of blank, were investigated and optimized by using Finite Element Analysis (FEA) through PAM-STAMP simulation software with the validated material model was based on Hill’s 1948 anisotropic yield criterion with Swift hardening law. The mechanical parameters in the mentioned model were derived from the results of uniaxial tensile tests. In conclusion, both the hydraulic cushion's blank holder pressure and the initial size of the blank were found to influence the thinning of the part, either individually or in combination. Despite optimizing both parameters, they were unable to consistently achieve the desired limit.

Abstract: In this work the relationship between changes in wafer center bow after thinning process and the wafer morphology has been shown. KOH wet etching allowed the observation and counting of dislocation in 4H-SiC substrate. In deep a correspondence between changes in wafer center bow and the dislocation density of the SiC substrate has been observed. By using a counting software, a relationship with the basal plane dislocation and center bow has also been observed.

Abstract: The present paper shows a new fixed abrasive bond-grit formulation aimed for best-in-class, low-cost and high-quality finished SiC wafer surfaces. Grinding wheels manufactured with this technology can accomplish ultra-smooth SiC (Ra = 0.55 nm and TTV < 1 μm) surfaces due to their unique bonding structure and their tailored grit size. Additionally, SiC wafers ground with these wheels exhibit reduced sub-surface crystal damage, mirror-like polished surface and improved wafer geometry while both the grinding forces and the wheel wear are kept low.

Abstract: Adapter parts are common in hydraulic pipelines. They can connect pipes of different cross-sections. The article discusses the crimping of pipes. Its peculiarity is that the pipe section to be crimped undergoes thinning, which is ensured by the gap between the tools. This process was studied to determine the deformation forces and the influence of various parameters of the operation on its value.

Abstract: To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin silicon carbide (SiC) wafers with a high removal rate by conventional mechanical processing because their hardness and brittleness cause cracks and chips during thinning. Therefore, the authors have attempted to thin SiC wafers using plasma chemical vaporization machining (PCVM), which is plasma etching using high-pressure plasma. PCVM has a high removal rate because of the high radical density in the high-pressure plasma, and it does not form a damaged layer on the processed surface because of the low ion energy. The authors have already achieved a very high removal rate of 15.6 μm/min by PCVM. However, many etch pits were generated on the wafer during PCVM in these high-speed machining conditions. Therefore, this study, using molten potassium hydroxide (KOH) etching, investigated the cause of such etch pits and found that they may stem from threading screw dislocation in the wafers. In addition, this research considered a process for reducing an etch pit size and succeeded in doing so by controlling wafer temperature.

Abstract: Around 70% of the cost in piping industry is spent in the pipe manufacturing with optimum design of pipes without defects. Research on design of pipes has gained importance from the last decade. There are numerous methods being developed to improve the efficiency of piping units considering various parameters. The pipe tends to flatten when they are forced to bend, this geometrical changes has a significant role in the acceptability criteria of pipes. It is necessary to bend pipes in order to transmit liquid or gas from one place to other place. In this work special attention is given to pipe bends because of high stress concentration due to various loading conditions. From several kinds of piping systems, process piping systems are chosen for analysis since pipes used here transport important and hazardous materials. Damage to such piping system can cause serious loss to economy and human lives. The geometrical imperfection associated with bending of pipes is ovality. This degree of ovality determines the acceptance of pipes. Thickening and thinning effects cause additional problems like large plastic deformation and loss of flexibility respectively. Hence estimation of the best degree of ovality is required. In this work effect of ovality is estimated by taking the internal fluid pressure and In plane bending moment into account.

Abstract: On the basis of ANSYS/LS-DYNA, the finite element model of incremented forming of conical part was constructed. The plastic deformation area of blank was increased and crack was delayed in multistage. Forming parts with the angle of 90°use multistage forming. Focused on the investigation of the influence of process parameters on the thinning rate and the thickness distribution then least-square response surface method was adopted to set up the approximate optimization model for thinning. The optimization on the approximate model was carried out using sequential quadratic programming method. The results show that the experimentally thinning rate is consistent with the theoretic result based on the homogeneous thickness distribution.