آہ! مولانا عبداﷲ عباس ندوی مرحوم
۱۰؍ دسمبر کے ’’تعمیر حیات‘‘ سے معلوم ہوا کہ مولانا عبداﷲ عباس ندوی اب روبہ صحت ہیں، اسی شمارے میں پروفیسر عبدالحلیم ندوی مرحوم کے متعلق خود مولانا کا ایک تعزیتی مضمون بھی نظر سے گزرا جس میں انہوں نے لکھا کہ پروفیسر مرحوم ان سے ایک سال سینئر اور مولانا معین اﷲ ندوی کے ہم درس تھے، ساتھ میں مولانا ظہور پرتاب گڑھی، مولانا عبدالغفار ندوی اور مولانا ابوالعرفان خاں ندوی بھی تھے، ان احباب کو یاد کرتے ہوئے لکھا کہ اب شائد ہی کوئی اس گروہ میں باقی رہا ہو، جو زندہ ہیں وہ کشتہ تیغ حیات ہیں، ان سطروں کو پڑھتے وقت کیا خبر تھی کہ کشتگان تیغ اجل کی مرثیہ خوانی کرنے والے کا ماتم اس قدر جلد کیا جائے گا، مولانا عرصے سے بیمار تھے اور ایک دن مخدوم گرامی مولانا تقی الدین ندوی کے فون سے معلوم ہوا کہ اب حالت بڑی تشویش ناک ہے، دو روز بعد وہ جنوری کے اخباروں میں ان کی وفات کی خبر آگئی اور اس طرح قریب اسّی (۸۰) سال پر محیط ایک اہل دل، صاحب اخلاص، دیدہ ور اور دردمند انسان کی داستان مکمل ہوگئی، اِناﷲ وَاِنا اِلیہ رَاجِعونْ۔
پھلواری شریف ان کا مولد ہے، ابتدائی تعلیم کے بعدوہ ندوے آگئے، جہاں مولانا سید ابوالحسن علی ندوی اور شاہ حلیم عطا جیسے اکابر کی سرپرستی اور مولانا سید سلیمان ندوی کی توجہات نے ان کے مستقبل کی راہوں اور منزلوں کو متعین کردیا، فراغت کے بعد ندوے میں قرآن مجید اور لغت قرآن کریم کی تعلیم و تدریس سے ان کے علمی سفر کا آغاز ہوا، بعد میں وہ ندوے کے ادیب اول ہوئے، برطانیہ میں لیڈس یونیورسٹی سے لسانیات میں پی ایچ ڈی کی سند حاصل کی، سعودی عرب میں نشریات کے ادارے سے وابستہ ہوئے، رابطہ...
Stress corrosion cracking (SCC) refers to the damage of mechanical components which are under the combined action of static load and corrosive environment. This phenomenon occurs in various applications including naval and aerospace industry where aluminum and steel alloys experience mechanical loadings in the presence of corrosive environments. In this research work, microstructural and environmental influence on corrosion behavior of Al-6061-T6 at different static loads was investigated. A new test fixture was developed for stress corrosion cracking. Dog-bone shaped tensile specimens of Al-6061-T6 were manufactured using CNC milling machine. Tests were conducted at constant loads of 200 N, 500 N and 800 N, in three different environments: dry ambient conditions, distilled water and 3.5% NaCl solution. Testing continued for different intervals of time i.e. 96 hours, 68 hours and 4.5 hours respectively. After each set of experiments, specimens were observed for cracks using metallurgical microscope. Detailed fractographic investigation of all the tested specimens was carried out using Scanning Electron Microscope (SEM). Excessive corrosion and material degradation was observed in specimens tested in distilled water and 3.5% NaCl environments.
Microstructural analysis depicted pitting corrosion and crack deformation. Some regions clearly showed that grain boundaries were attacked due to oxidation and chemical attack causing weakening of grain boundaries and resulted into intergranular corrosion. Precipitates and grain boundaries in Al-6061-T6 served as a reason of crack initiation due to hydrogen diffusion. Fractographic investigation provided the evidence of trans granular fracture as well as intergranular fracture which was observed as dimples and extensive ductile tearing.
The present PhD dissertation has completed research on results related to flow behavior due to shear stress on the boundary of some Newtonian and non- Newtonian fluids under different circumstances. Firstly, we have discussed some concepts related to Newtonian and non-Newtonian fluids, constitutive equations, equations of motion and integral transforms. Secondly, we have presented the exact solutions of velocity, temperature and shear stress fields corresponding to some flows of Newtonian, second grade, Maxwell and Oldroyd-B fluids. We have established general solutions for the unsteady free convection flow of an incompressible viscous fluid due to an infinite vertical plate that applies a shear stress f (t) to the fluid, when thermal radiation and porous effects are considered. These general solutions may generate a large class of exact solutions corresponding to different motions with technical relevance. Some special cases are investigated under the effects of pertinent parameters on the fluid motion. Unsteady motion of second grade fluids induced by an infinite plate that applies a time-dependent shear stress f (t) to the fluid is also studied. General solutions may be reduced to new solutions of Newtonian fluids or they may be used to obtain known solutions from the literature. Furthermore, in view of an important remark, general solutions for the flow due to a moving plate may be developed. We have also studied the Couette flows of a Maxwell fluid caused by the bottom plate applying shear stress on the fluid. Exact expressions for velocity and shear stress corresponding to the fluid motion are determined using the Laplace transform. Two particular cases with constant shear stress on the bottom plate or sinusoidal oscillations of the wall shear stress are further discussed. Some important charac- teristics of fluid motion are highlighted through graphs. The unsteady motion of an Oldroyd-B fluid over an infinite flat plate is studied by means of the Laplace and Fourier transforms. After time t = 0, the plate applies cosine/sine oscillating shear stress to the fluid. The solutions obtained are presented viii as a sum of steady-state and transient solutions, which may easily be reduced to the similar solutions corresponding to Newtonian or Maxwell fluids. A central issue namely, obtaining the time for which the steady-state is reached is address by means of numerical calculations and graphical illustrations. The influence of oscillations frequency or of material parameters on this time corresponding to the steady-state is also analyzed. It is lower for cosine oscillations in comparison to sine oscillations of the shear, decreases with respect to ω and λ and increases with regard to λr .