scholarly journals Prediction of Ductile Damage and Fracture in the Single and Multi-stage Incremental Hole-flanging Process Using a New Damage Accumulation Law

2021 ◽  
Author(s):  
Seyyed Emad Seyyedi ◽  
Hamid Gorji ◽  
Mohammad Javad Mirnia ◽  
Mohammad Bhakhshi-Jooybari
Keyword(s):  
Damage Accumulation ◽  
Single Point ◽  
Alloy Sheet ◽  
Fracture Prediction ◽  
Fem Model ◽  
User Subroutine ◽  
Damage And Fracture ◽  
Multi Stage ◽  
Non Linear ◽  
Hole Flanging

Abstract Incremental hole-flanging (IHF) is a process in which a sheet with a pre-cut hole is flanged by the single point incremental forming (SPIF) process. Fracture prediction in IHF, such as SPIF, is associated with many challenges due to the deformation mechanisms. The purpose of this paper is to overcome the existing limitations and challenges, and thus, to predict accurately failure in single, and multi-stage IHF processes. To this end, the modified Mohr-Coulomb (MMC) criterion was implemented using an appropriate user subroutine in a finite element method (FEM) model. The AA6061-T6 aluminum alloy sheet, which has low formability, and is fractured from its free edges in the IHF process, was examined as an example. Initially, a linear damage accumulation law, in which the prediction error is high due to the non-linear stress and strain states in the IHF, was used to predict the fracture. Therefore, in the next step, a non-linear damage accumulation function was utilized. While the non-linear accumulation accurately predicts the single-stage IHF fracture, it is not able to predict the fracture well in the multi-stage IHF. It was observed that in multi-stage IHF, the rate of damage accumulation decreases with increasing the number of forming stages. Accordingly, a new non-linear damage accumulation rule was developed. Experimental and numerical results indicated acceptable accuracy of the proposed non-linear accumulation in the fracture prediction in the single and multi-stage IHF process.

Simulation of Multi-Stage Compressor at Off-Design Conditions

2017 ◽  
Author(s):  
Feng Wang ◽  
Mauro Carnevale ◽  
Luca di Mare ◽  
Simon Gallimore
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Eddy Viscosity ◽  
Turbulence Models ◽  
Viscosity Model ◽  
Eddy Viscosity Model ◽  
Multi Stage ◽  
Pressure Profiles ◽  
Non Linear ◽  
The Right

Computational Fluid Dynamics (CFD) has been widely used for compressor design, yet the prediction of performance and stage matching for multi-stage, high-speed machines remain challenging. This paper presents the authors’ effort to improve the reliability of CFD in multistage compressor simulations. The endwall features (e.g. blade fillet and shape of the platform edge) are meshed with minimal approximations. Turbulence models with linear and non-linear eddy viscosity models are assessed. The non-linear eddy viscosity model predicts a higher production of turbulent kinetic energy in the passages, especially close to the endwall region. This results in a more accurate prediction of the choked mass flow and the shape of total pressure profiles close to the hub. The non-linear viscosity model generally shows an improvement on its linear counterparts based on the comparisons with the rig data. For geometrical details, truncated fillet leads to thicker boundary layer on the fillet and reduced mass flow and efficiency. Shroud cavities are found to be essential to predict the right blockage and the flow details close to the hub. At the part speed the computations without the shroud cavities fail to predict the major flow features in the passage and this leads to inaccurate predictions of massflow and shapes of the compressor characteristic. The paper demonstrates that an accurate representation of the endwall geometry and an effective turbulence model, together with a good quality and sufficiently refined grid result in a credible prediction of compressor matching and performance with steady state mixing planes.

scholarly journals Impact Size and Determinants of Indirect Cost of Financial Distress: Role of Receivable and Inventory Management

2020 ◽  
Vol 16 (2) ◽  
pp. 179-207
Author(s):  
Umar Farooq ◽  
Muhammad Ali Jibran Qamar ◽  
Krishna Reddy
Keyword(s):  
Indirect Cost ◽  
Inventory Management ◽  
Financial Distress ◽  
Multi Stage ◽  
Initial Stage ◽  
Non Linear ◽  
Management Policies ◽  
Internal Operations ◽  
The Impact

This research investigates the opportunity cost as an indirect cost of financial distress from two perspectives. First, indirect cost is estimated using multi-stage financial distress and non-linear proxy of debt. Second, receivable and inventory management are studied as determinants of indirect cost. The sample includes ongoing Pakistani firms that were healthy in the previous year and documenting positive gross profit. Results showed that firms bear opportunity loss primarily due to leverage rather than multistage financial distress. However, a non-linear relationship is found between leverage and indirect cost. Results further explored the impact of multistage financial distress on internal operations, i.e., working capital policies. It is found that firms manage receivable and inventory simultaneously during the multistage financial distress. Results revealed that increasing receivables and decreasing inventory is suitable during the transition of healthy firms to initial stage of financial distress, i.e., profit reduction. However, decreasing receivables, along with holding more inventory, is recommended for healthy firms that face liquidity problems subsequently. It is concluded that managers can reduce the indirect cost after deploying the optimal debt ratio and recommended receivable and inventory management policies.

Non-linear damage accumulation in Au-irradiated SrTiO3

2006 ◽  
Vol 251 (1) ◽  
pp. 127-132 ◽  
Author(s):  
Y. Zhang ◽  
W.J. Weber ◽  
V. Shutthanandan ◽  
S. Thevuthasan
Keyword(s):  
Damage Accumulation ◽  
Non Linear
Sign in / Sign up

Export Citation Format

Share Document