Damage Mechanics Based Approach In Failure Prediction Of Draw Forming Processes

Permanent Magnet Synchronous Motor (PMSM) drives with a high degree of fault tolerance are required where it is crucial to guarantee continuous operation of the drive system. To have additional benefits during a fault, PMSM drives with open-ended winding can be employed. Both ends of the windings in the prototype PMSM are connected to a dual inverter arrangement of two 2-level inverters both connected to one dc source. However, considering the zero sequence voltage is clamped to zero because of the return path between the two inverters, zero sequence current circulates in the machine windings which increases losses and generates heat. Furthermore, most PMSMs generate harmonics in the back electromotive force. These harmonics if not compensated for will couple with the circulating zero sequence current, increasing the machine current further and typically beyond ratings, the total harmonic distortion of the current will increase, and the generated torque oscillates more than twice the average torque. To accurately control the current during normal operating conditions, the flux linkage harmonics are measured and incorporated with the dq0-axis current control scheme to restrict the harmonic current in the system. A revised simulation model for the PMSM drives was constructed that considers the zero sequence model and integrate the effects of nonsinusoidal back EMFs within the drive. The model can be easily extended to higher harmonic based on the obtained harmonics of the PMSM drives. Open-phase faults are then considered in this thesis. Semiconductor switches in a phase leg can be turned off and the phase winding disconnected so that the system effectively operates under two-phase vector control. A simple modified transformation under fault conditions is proposed that enables the current to be regulated in the dq-axis and retains control of the voltage. The different outcomes of utilizing a system that maintains 1200 between phase currents and a phase shift of 600 between the remaining healthy phases are investigated. Under such conditions, possible switching states that can be used are considered. The results demonstrate that the proposed modified coordinate transformation is easy to implement and effective in solving the loss of one phase when open-phase fault occurs in the setup. The performance evaluation based on the experimental measurements are investigated during normal and faulted operating conditions

Damage mechanics based approach in failure predication of draw forming procecesses

In a cup draw forming operation, the desired shape results from the material hardening process under controlled plastic deformation and the springback phenomena. In this study, a mechanics-of-deformation approach is developed based on damage variables and large plastic deformation. The approach is then employed to estimate the onset of the material damage event and the location of fracture based on the mechanics response of the metal blank. Draw forming behavior of low carbon steel is examined as a case study. The loading rate is conducted at a slow loading response of the steels in the large deformation of the draw forming processes. Axisymmetric and 3D solid models are developed for finite element (FE) simulations to gain insight into the evolution of internal states and damage in the steel blanks during the draw forming process. In the FE simulation, Johnson-Cook constitutive model with isotropic hardening rule is employed. The Rice-Tracey ductile damage criterion is employed to indicate damage initiation event along with a linear energy-displacement relation for damage evolution rule. Results show that while the applied loading (tool displacement) is quasi-static corresponding to the strain rate of 0.001 sec-1, the maximum plastic strain rate at fracture could reach 100 times greater at the critical material flow region. Failure of the deforming steel blank is localized with excessive plastic deformation. While the onset of damage can be efficiently predicted using the axisymmetric FE model with damage-based model, the subsequent damage evolution of the localized ductile failure requires a 3D continuum FE model. The predicted tool load-displacement response is employed in validating the FE model. Effects of drawing parameters including drawing speed, blank holder force and die clearance on the resulting deformation of the drawn cup-shape part are established. Based on the response of the mechanics-of-deformation, the established failure prediction approach is proven more accurate and reliable

Environmetric study on air quality pattern for assessment in Northern region of Peninsular Malaysia

Background and Objective: Causes of air quality problems detected are emission from vehicles, industrial emissions and open burning. The objective of this study was to determine the significant pollutant parameters contributing to air quality problems and also to look at air quality pattern at 12 air monitoring stations in the Northern region of Peninsular Malaysia (Perlis, Kedah, Pulau Pinang and Perak). Methodology: The data set was given from the Department of Environment, Malaysia (DOE) for the years 2002-2012 (11 years). Basically, air pollution index (API) parameters such as O3, SO2, CO, NO2 and PM10 were involved in this study. Therefore, environmental metric techniques used such as cluster analysis (CA), perform three smaller groups compared 12 stations which has a same characteristic. This clusterization was also used to look air quality pattern based on yearly and specific monthly basis. It were shown that, 2005 and 2006 has a more stand out and different pattern. The third quarter of these years showed predominant and different pattern due to transboundary pollution. Discriminant analysis (DA) was used for differentiating each class. The study found that there were establish different variables, between each class. Principal component analysis (PCA), combined with factor analysis (FA), was used to know significant pollutant parameters based on five pollutants/gases in the air pollution index (API) which cause many activities either internal or external factors. Results: The study found that SO2, NO2 and O3 are the major pollutants contributing to degradation of air quality in the Northern region due to the combustion process from vehicles and industries. Conclusion: As a result of using the envirometric technique for analyzing huge data sets become better understanding air quality pattern and more clearly identify significant air pollutant parameters

Development of Polymeric Nanoparticles of Garcinia mangostana Xanthones in Eudragit RL100/RS100 for Anti-Colon Cancer Drug Delivery

Xanthones are a group of oxygenated heterocyclic compounds with anticancer properties, but poor aqueous solubility and low oral bioavailability hinder their therapeutic application. This study sought to prepare a xanthones extract (81

Design And Development Of Auto-Steel Draw Forming Test Device

This work is concerned with the design and development of draw forming test device with double action draw forming mechanism.This device is designed to operate on universal testing machine (UTM).The dual phase auto-steel about 1.2 mm thick is used as deformable blank.The double action mechanism is generated by an external hydraulic system to equally apply the blank holder force (BHF).Hence,the punch force is driven by UTM’s hydraulic system.The design load and die displacement is initially predicted by FE simulation at maximum load of 123kN and 14 mm displacement respectively.Draw forming result shows the fracture is recorded at 108 kN of punch force and 9.5 mm of displacement depth

Antiangiogenic properties of Koetjapic acid, a natural triterpene isolated from Sandoricum koetjaoe Merr

Background: Angiogenesis, the formation of new blood vessels, has become an important target in cancer therapy. Angiogenesis plays an important role in tumor growth and metastasis. Koetjapic acid (KA) is a seco-A-ring oleanene triterpene isolated from S. koetjape. The solvent extract of this plant species was shown previously to have strong antiangiogenic activity; however the active ingredient(s) that conferred the biological activity and the mode of action was not established. Given the high concentration of KA in S. koetjape, an attempt has been made in this study to investigate the antiangiogenic properties of KA.Results: Treatment with 10-50 μg/ml KA resulted in dose dependent inhibition of new blood vessels growth in ex vivo rat aortic ring assay. KA was found to be non-cytotoxic against HUVECs with IC40.97 ± 0.37 μg/ml. KA inhibited major angiogenesis process steps, endothelial cell migration and differentiation as well as VEGF expression.Conclusions: The non-cytotoxic compound, KA, may be a potent antiangiogenic agent; its activity may be attributed to inhibition of endothelial cells migration and differentiation as well VEGF suppression

Sexual dysfunction in patients with polycystic ovary syndrome in Malaysia

Background: Polycystic ovary syndrome (PCOS) is a combination of chronic anovulation, obesity, and hyperandrogenism and can affect sexual function in women of reproductive age. It is also associated with endometrial cancer. Our aim was to evaluate the frequency and predisposing factors of sexual dysfunction in PCOS patients. Materials and methods: In this cross-sectional study, 16 married women with a definite diagnosis of PCOS were recruited. Sexual function was assessed in the domains of desire, arousal, lubrication, orgasm, satisfaction and pain using the female sexual function index (FSFI) questionnaire. Patients were also assessed for mental health using the depression, anxiety and stress (DASS-21) questionnaire. Presence of hirsutism was assessed using the Ferriman-Gallwey (FG) scoring system. Demographic data were obtained from patients during in-person interview. Results: Sexual dysfunction was present in 62.5% of patients with the domains of arousal and lubrication particularly affected (93.8% and 87.5%, respectively). Patients with symptoms of depression and anxiety were significantly more likely to suffer sexual dysfunction than those without these symptoms (p=0.04 and p=0.03 respectively). Patients with stress symptoms reported higher orgasm dysfunction than those without (p=0.02). No significant difference in any of the FSFI score domains was observed between patients with and without hirsutism. Conclusions: PCOS patients markedly suffer from sexual dysfunction and therefore it seems appropriate to be screened for intervention. Poor mental health conditions that may be the result of infertility or other complications of PCOS should also be considered as curable causes of sexual dysfunction in these patients

Synergistic effects of activated carbon and nano-zerovalent copper on the performance of hydroxyapatite-alginate beads for the removal of As\u3csup\u3e3+\u3c/sup\u3e from aqueous solution

© 2019 Elsevier Ltd In this study, activated carbon (AC) and nano-zerovalent copper (nZVCu) functionalized hydroxyapatite (HA) and alginate beads were synthesized and used for the removal of As3+ from aqueous solution. The characterization by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, high resolution transmission electron microscopy, BET surface area analysis, thermogravimetric analysis, and Fourier transform infrared spectroscopy revealed successful formation of the AC/nZVCu/HA-alginate, nZVCu/HA-alginate, AC/HA-alginate, and HA-alginate beads. The scanning electron microscopy and surface analysis revealed the prepared beads to be highly mesoporous which led to the maximum adsorption of As3+, i.e., 13.97, 29.33, 30.96, and 39.06 mg/g by HA-alginate, AC/HA-alginate, nZVCu/HA-alginate, and AC/nZVCu/HA-alginate beads, respectively. The thermogravimteric analysis showed the nZVCu/HA-alginate beads to be highly stable while the AC composite beads as the least stable to heat treatment. The HA-alginate beads achieved 39% removal of As3+, however, removal efficiency was promoted to 95% by coupling AC and nZVCu with HA-alginate beads at a reaction time of 120 min. The removal of As3+ by the prepared AC & nZVCu coupled HA-alginate beads was promoted with increasing [As3+]0 and [AC/nZVCu/HA-alginate]0. The pH of aqueous solution significantly influenced the removal of As3+ by AC/nZVCu/HA-alginate beads and maximum removal was achieved at pH 5.8. Freundlich adsorption isotherm and pseudo-second-order kinetic models were found to best fit the removal of As3+ by the synthesized beads. The high performance of AC/nZVCu/HA-alginate beads in the removal of As3+ even after seven cyclic treatment as well as least leaching of Cu ions into aqueous solution suggest enhanced reusability and stability of HA-alginate beads by coupling with AC and nZVCu. The results suggest that the synthesized beads have good potential for the removal of As3+ from aqueous solutions

Influences Of Draw Forming Process On The Crash Analysis Of A Circular Cup

The change of a structural part that occurred after forming process can affect crash response. Current industrial practice only utilizes the geometry in crash analysis. This study investigates the effect of forming histories of a circular cup formed by draw forming process in the crash simulation. Crash analysis at an initial velocity of 50km/h was performed using the explicit finite element code Radioss. The Johnson-Cook constitutive material model was used to characterize the material properties of advanced high strength steel DP600. Crash simulations are conducted in two different cases using a geometrical cup model with case 1 no forming history and case 2 all forming histories obtained from forming process. Results from this study indicate that the mechanical response of steel DP600 in a crash differ by 80.7 % for contact force and 5.87% for energy absorption when forming effects were considered. The contact force tends to increase more with displacement in case 2 compared to case 1. The non-uniform thickness and work hardening from forming process do alter significantly the crashworthiness of a structural part in the subsequent crash event