البحث — المستودع الرقمي العراقي

نتائج البحث: 25 من أصل 10,697

دراسة مقارنة بين T - spline وNURBS في النمذجة والتشغيل باستخدام ماكنة التفريز المبرمجة Comparison Study of T - Spline And NURBS In Modeling And Machining Using CNC Milling Machine

اسم المؤلف: مهند مصدق جعفر

اسم المشرف: ليث عبد الله محمد

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة الانتاج

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: نمذجة السطوح باستخدام تقنية الـ (T - spline ) تعد من اهم الوسائل المتسخدمة الان في التصميم المعان بالحاسوب (CAD).يهدف البحث الى زيادة الانتاجية من المنتجات المعقدة من خلال تعزيز عملية النمذجة السطحية للمنتج وتعزيز التصنيع باستخدام T - SPLINE للنمذجة السط | Surface modeling utilizing T - spline technique is one of the most important tool now in computer aided design (CAD).ThisThesisaims to increase the productivity of complicated products through enhancing the process of product surface modeling and manufacturing by using T - spline for surface modeling. This method provides the designer with many powerful tools to add details only where necessary on the CAD modeling, create non - rectangular topology of the surface, easily edit complex freeform models, and besides maintaining NURBS (non - uniform rational B - splines) compatibility of the model.ThisThesisuses T - spline for surface modeling and compare it with NURBS modeling to get the best modeling points between the two methods. The comparison will be through surface analysis and manufacturing process.ThisThesisincludes design of two types of models : convex model (bicycle seat) and concave model (longitudinal section of the bottle) for each T - spline surface and NURBS surface using Rhinoceros 5.0 software which has been transformed to UG - NX8.5 software to get the machining process simulation and G - code programs for the models. The models have been machined using 3 - axis vertical CNC machine (C - tek) type.Finally, analysis of surfaces (Environment Map analysis, Zebra analysis, Naked Edges analysis, Gaussian Curvature analysis, data structure analysis, Draft Angle analysis) by Rhinoceros 5.0 software and measurement of the roughness by Pocket Surf equipment and measurement runtime for machining by timer, shows that the T - Splines surfaces typically have (50 - 70%) less geometric data structure [ surfaces , 3d curve , 2d curves , vertices , edges , trims , loops , faces ] than the equivalent NURBS surface, inEnvironment Map analysis, the image of T - Spline surface for the models is reflected moreclearly than a NURBS surface, in Naked Edges analysis, the T - Spline surface for the models has a number of naked edge less than the NURBS surface, in measurement runtime for machining (roughing and finishing), the T - spline surface for the bicycle seat model is machined in (16 minutes) less than machining the NURBS surface, and the T - Spline surface for the longitudinal section of the bottle model is machined in (10 minutes) less than machining the NURBS surface. In measurement of roughness, the T - Spline surface for the bicycle seat model has (2.4861 µm) average (Ra) for patches measured roughness average (Ra), and the NURBS surface has (4.9216 µm) average (Ra) for patches measured roughness average (Ra).

تحليل مسار العدة في عملية التشكيل التزايدية للصفائح المعدنية Analysis of Tool Path In Incremental Sheet Metal Forming Process

اسم المؤلف: ميثم سعد علي

اسم المشرف: وسام كاظم حمدان

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة الانتاج

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: التشكيل التزايدي للصفائح المعدنية هو عملية مرنة للغاية ومتعددة الاستعمالات للتصنيع السريع لاجزاء الصفائح المعدنيه المعقدة حيث تمتلك امكانية التكيف بامتياز مع انظمة التحكم الرقمي بالحاسوب (مكائن التفريز المبرمج CNC) من خلال السيطرة المباشرة على بيانات CAD | Incremental sheet forming (ISMF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. It has excellent adaptability to computer numerical control (CNC) systems through direct control of CAD data, minimizing the use of specialized tooling and presses. A sheet of metal is formed by a progression of localized plastic deformation using simple forming tool controlled by a CNC machine - tool. The aim of the presented thesis is to investigate the feasibility of incrementally forming of 3D complex shape (like automotive heat shield shape) and the solar cooker shape by Single Point Incremental Forming process without using a dedicated die depending on different tool paths. Six different forming tool paths (unidirectional ZLVTP, bidirectional ZLVTP, FPRTP, ZGZTP, BSLTP and HSLTP) were generated byUnigraphics - NX8 (UGS - NX8) programing system and applied to realize solar cooker shape and automotive heat shield shape. The feasibility investigation and development of automotive heat shield shape is based on three control factors are tool path type, forming tool head shape and the Z - increment (vertical pitch). For each of these factors, levels were tested. The tool head shape and vertical pitch contain their both on two levels while the tool path type on six levels. Hence, 24 experiments applied to realize automotive heat shield shape based on a full factorial design of experiments, and 6 experiments applied to realize solar cooker shape. Hybrid tool paths are tested to explore the applicability these paths in ISMF process. This thesis discussed the impact of tool paths types and other control factors (tool shape and vertical pitch) on the three different quality characteristic namely geometrical accuracy, thickness variation and forming time. The significant of the control factors are explored using two statistical methods are analysis of variance ANOVA and main effect plot. All experiments were carried out on sheets of Aluminum Alloy (AL1070) with thickness 1.5 mm by using 3axis CNC machine. The CNC machine and dial gauge are used to measure dimensional accuracy and final thickness of formed parts respectively. Depending on the results of this work, Helical - Streamline tool path (HSLTP) and follow periphery tool path (FPRTP) are achieved higher geometrical accuracy when forming the solar cooker shape and the automotive heat shield shape respectively. On the other hand, Z Level profile tool path (ZLVTP) is the best tool path to achieve homogeneous thickness distribution and minimum forming time of formed parts. Hybrid tool paths are undesirable in incremental sheet metal forming. The ANOVA results show that all control factors have influence on the accuracy, especially the tool path type. The tool shape and vertical pitch have no influence on the thickness of the formed parts. But, the vertical pitch has major effects on the forming time and accuracy. In contrast, the tool path shape has a great influence on the process implementation.

التحقيق التجريبي والعددي للصفائح الرقيقة المثقوبة تحت الشد Experimental And Numerical Investigations of Thin Tensioned Plates With Holes

اسم المؤلف: ارشد عبد الله راشد

اسم المشرف: كريم محسن يونس

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة الانتاج

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: ان الصفائح المثقوبة تستخدم عالميا في تصنيع الھياكل في التطبيقات الميكانيكية والانشاءات كمثال على ذلك ھياكل الطائرات والتراكيب الطبية ووصلات الربط الخ. ومن المعروف جيدا ان استعمال الثقوب في الھياكل المجھدة تولد اجھادا موقعيا عاليا في منطقة من الثقب تعرف بم | The plates with holes are used in cosmopolitan for manufacturing structures in mechanical and civil engineering applications like aircrafts, medical structures, joint connection applications etc. It is well known that utilizing holes in stressed structures produces highly localized stresses at area of the holes known as the stress concentration area,which leads to reduce the mechanical strength of the structures.The main objective of this study is to investigate the effect of three parameters on the stress concentration factor in plate with two holes having different size holes and subjected to uniaxial tension. The three parameters include firstly, the location of holes when oriented with respect to axis of loading, parallel, transverse and inclined with line of uniaxial tension load at different angles. Secondly, the aspect ratio for the hole size (large to small radius).The last parameter effect is the distance between two holes.Numerical simulation using finite element method for two - dimensional model is developed to determine the maximum value of Von Mises stress with commercial software package ANSYS V.11.The experimental photoelastic technique is carried out on fabricated polycarbonate model loaded in one direction. From the analysis of the results, it is found that the maximum stress concentration factor is at the point tangent to the edge of the hole. The comparison between the finite element method and experimental photoelastic technique results showed the stress concentration factor, which obtained experimentally and with finite element method are congruent, since the maximum variation between the two results is about 7.03% As well as the highest and lowest value of the stress concentration factor equal to 3.1973, 2.0640 at value of angle 60°, 90° respectively.It is recommended from the above conclusions that manipulating the three parameters which effect the stress concentration factor are namely, holes position, size, and distance between two holes on the plate that used in the application will play essential role to reduce the value of stress concentration factor which subsequently crucially minimize or avoid fast failure. This can be translated into saving precious lives preventing money wastage due to structures damage ending into catastrophe.

فحص بلى عدة القطع المعان بالرؤيا الحاسوبية خلال عملية الخراطة Computer Vision Aided Inspection of Cutting Tool Wear In Turning

اسم المؤلف: علي كريم علوان العكيلي

اسم المشرف: علي عبار خليف

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة الانتاج

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: في الوقت الحاضر , تحظى مكائن القطع المبرمجة باھمية كبيرة في المعامل والورش التصنيعية بسبب دقتھا العالية ومرونتھا لكن لسوء الحظ لا تزال ھذه المكائن غير قادرة على التاكد من جودة السطوح المنتجة. الاتجاه نحو اتمتة عمليات القطع سير للحاجة الملحة للحصول على ج | Nowadays, computerized numerically controlled (CNC) machines have high importance in manufacturing factories and workshops due to their high accuracy and flexibility. Unfortunately they still cannot ensure the quality of machined products. The trend towards automation in machining has been driven by the need to maintain high product quality with improving production rate, these improvements can be possible by monitoring and control of machining process. In this research a vision based monitoringsystem was introduced for the on - line direct automated measurement of the cutting tool flank wear width based on a new algorithm on the basis of canny edge detection and morphological operations for the captured images.Twelve specimens were prepared using STARCHIP CNC turning with four cutting speeds (57,98,110 and 125 m/min) and three depths of cut (0.5,1 and 2 mm) and constant feed of (0.04 mm/rev). Maximum and minimum absolute error and error percentage in the maximum flank wear width was (0.058,0.002 mm) (9.7,0.54 %) respectively. The results show the effectiveness of the proposed method in the monitoring of the tool condition.Also, Vision based monitoring system was proposed for the measurement of tool nose wear which have direct interaction with the workpiece during machining. Measurement operation is done by comparing reference and worn tool images; the algorithm is composed of image preprocessing, Otsu thresholding, conforming method for the exact alignment between the two images and image subtraction is performed in order to detect the nose wear area. Morphological opening by reconstruction was used to remove isolated foreground pixels result in due to the quantization errors. The maximum and minimum error percentage in tool nose wear area (6.72,0.48 %) respectively; the experimental results show that nose wear occurs after the flank wear exceeded its maximum standard limit in roughing operations Keywords : tool wear, flank wear, nose wear image processing, automated visual inspection, tool condition monitoring.

دراسة سلوك البلى الانزلاقي الجاف لسبائك المنيوم - 7% سليكون عمليا وباستخدام تقنية تصميم التجارب Studying Dry Sliding Wear Behavior of Al - 7% Si Alloys Using Experimental And DOE Techniques

اسم المؤلف: قاسم سعد عبد الواحد

اسم المشرف: عقيل ظاهر صبحي علي عبار خليف

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة المعادن

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: تعد سبائك الالمنيوم - سليكون والتي تحتوي على التيتانيوم احدى المواد التي تتميز بمقاومتها للبلى كما بينت الدراسات والابحاث العلمية ذلك.في هذا البحث تم صب سبيكة المنيوم - 7% سليكون وبنسب مختلفة من التيتانيوم (0.5 , 1 , 1.5%) وتحت معدلات تبريد مختلفة في قال | Aluminum - silicon alloys that contain Titanium can be considered one of the wear resistant materials and attract several researchers recently.In this work ,Al - 7%Si alloy with different percentages of Ti ( 0.5 , 1 , 1.5% ) was poured under different solidification conditions into the metal mould.All prepared alloys were dry slided under different bearing pressures ( 5 , 10 , 15 , 20 , 25 N ) on the steel counterface surface using pin on disk wear apparatus. Optical microscope and scanning electron microscope (SEM) were used to study the microstructure and determine wear mechanism of Al - Si alloys respectively. On the other hand , X - ray diffraction technique (XRD) was used to determine the phases that were present in the matrix of Al - Si alloys.Microstructural analysis and X - ray diffraction showed that two phases are presented in the matrix of Al - 7%Si alloys.These phases are ? - aluminum and eutectic and three phases are present in the matrix of Al - Si alloys that contains Ti. These phases are ? - aluminum ,eutectic and titanium aluminide Ti9Al23.Significant refinement occurred for ? - aluminum, eutectic and titanium aluminide Ti9Al23 phases when using metallic mould cooled with cold water in comparison with heated and unheated metallic moulds Hardness was increased with increasing Ti percentage and with increasing the severity of solidification condition used.Remarkable changes in the wear rate occurred for Al - Si alloys during dry sliding in which the magnitude of wear rate was dependent on the Ti percentage ,load and solidification condition used.Design of experiment (DOE) was used to optimize the effect of process variables ( load and Ti percentage) on the wear rate under different solidification conditions using computational statistical software (Mintab 16).

تاثير التشكيل على البنية المجهرية وسلوك البلى للمواد المعدنية المتراكبة النانوية Al2O3 / A356 The Role of Forming On Microstructure And Wear Behavior of Metal Nano Composite Al2O3 / A356

اسم المؤلف: مروان باسل حسين

اسم المشرف: نوال عزت عبد اللطيف عقيل ظاهر صبحي

الموضوع العام: هندسة الانتاج والمعادن والمواد

السنة: 2014

الموضوع الدقيق: هندسة المعادن

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: في هذا البحث تم تحضير المواد المركبة النانوية اساس معدني (A356/Al2O3) باستخدام تقنية (rheocasting) ومن ثم تم اجراء عملية التشويه على الساخن عند درجة حرارة °250 م.في البداية تم صهر السبيكة A356 في درجة حرارة °730 م بعدها تم تبريدها الى درجة حرارة الشبه ص | In the present work Al2O3/A356 nano composites have been prepared using rheocasting technique, the nano composites were then processed using hot deformation at 250 °C.Firstly A356 matrix alloy was melted at about 730 °C, the superheated molten alloy was allowed to cool to the semi - solid temperature at 600 °C, then Al2O3 nano - particles with different size (10,20) nm and different weight percentages (1 and 2)%wt were added inside the vortex formed due to stirring , hot deformation carried out with different ratio 30% and 40% at the temperatures of 250 °C and strain rates 0.1 s?1. The produced nano composites samples were characterized using optical and scanning electron microscopy ,X - ray diffraction , hardness test and wear test using pin on disc apparatus. The results of microstructural observations showed that the Al2O3 nano particles cluster mostly near the grain boundaries and form a band surrounding the grain boundaries. The dendritic structure of ? - Al phase is fragmented and the ? grains became more uniform and smaller than their corresponding as - cast 356 alloy. On other hand the microstructures of nano - Al2O3/A356 composites after casting and hot deformation at 250°C, showed modification of ? - Al and Si eutectic. The columnar dendrites ? - Al phase changed to the nearly equiaxed grains or globular morphology. The results of hardness test showed that the nano Al2O3/A356 composite were exhibited higher hardness than the as - cast A356 alloy The nano - composites hardness, increase with increases the size and increases in weight percentage of the Al2O3 nano - particles, and with increasing percentage deformation. The result of wear test showed that the hot deformed nano Al2O3 /A356 composites have greater wear resistance compared with hot deformed A356 alloy. Furthermore, with increasing the particle size and the percentage of Al2O3 nano particles, wear rate will decrease. The results also revealed that the optimal results was achieved at the nano - composites containing 20nm Al2O3 particles after hot deformation with 40%. SEM studies of the worn surface of nano composites showed that the main wear mechanism was oxidative in conjunction with metallic wear.

كلال الدورات المنخفضة في سبيكة المنيوم قابلة للتصليد بالترسيب Low Cycle Fatigue of Precipitation Hardened Aluminum Alloy

اسم المؤلف: سيف خالد محمود

اسم المشرف: ظافر صادق الفتال

الموضوع العام: هندسة الميكانيك

السنة: 2014

الموضوع الدقيق: ميكانيك تطبيقي

الدرجة: ماجستير

الجامعة: الجامعة التكنولوجية - قسم الهندسة الميكانيكية

اللغة: الانكليزية

مكان الجامعة: بغداد

الصفحات الاولى:

المستخلص: لسبائك الالمنيوم عالية المقاومة طيف واسع من التطبيقات من صناعة السيا ا رت الى الصناعات الفضائية.ان السبب الرئيسي وراء النمو السريع للطلب على هذة السبائك هو مزيج من الخواص الفريدة التي جعلت منها واحدة من اكثر الت ا ركيب والمواد الهندسية استعمالا، ولذلك ل | High strength AL - alloys have a wide spectrum of applications from automobile to aerospace industries. The demand for these aluminum alloys grows rapidly because of the unique combination of properties which make them the most versatile of engineering and construction materials. Hence, development of high strength Al - alloys continues to be an important area of research.In this work, the influence of different heat treatments on the mechanical properties and fatigue life under low cycles of wrought 7075 aluminum alloy was experimentally investigated. The heat treatments included peak ageing (T6), over ageing (T73) and annealing (O).The effect of heat treatments on the alloy was explained in terms of their influence on the mechanical properties. The results showed that T73 temper has an ultimate strength of 504.7 MPa and elongation of 12.5%. Peak ageing treatment enhanced the strength by 10.9% and reduced the elongation by 7.2%, while in the annealed condition, the strength was reduced and the elongation was improved by 51.33% and 31.2%, respectively. T6 had the highest hardness followed by T73 and O tempers.The flat fatigue specimens were subjected to constant reverse bending load. The tests were performed at the laboratory environment with a frequency of 23.3 Hz and at a stress ratio (R) of - 1. For each temper, strain - life graphs were obtained for specimens with notches in the form of central cylindrical holes made by drilling. The fatigue resistance of specimens with notches was compared to the results for notch - free specimens. It was observed that the presence of a stress raiser, such as a drilled hole, lowers the fatigue life for all tempers. However, the notch sensitivity of the fatigue life was different for each temper.The fatigue crack growth rate of T73 and annealed temper was investigated, the results showed that T73 treated sample exhibits higher crack growth resistance. Paris` equation was derived for each temper Keywords : LCF. precipitation hardening. 7075 aluminum alloy. fatigue crack growth.