20525

۲۰۵۲۵

طراحي و ساخت قطعات آزمونه براي تست NDT بوسيله تكنولوژي توليد افزايشي (AM)

كارشناسي ارشد

طراحي كاربردي

1395-1397

۱۳۹۷/۱۲/۱۱

دكتر محمد رياحي

مكانيك

با ورود فناوري توليد افزايشي فلزي به دنياي صنعتي، يكي از بزرگ¬ترين آرزوهاي صنعتگران كه توليد مستقيم قطعات از مدل كامپيوتري بود، به حقيقت پيوست. اين فناوري رو به رشد بسيار پويا و فعال بوده و همه روزه شاهد ورود آن به صنايع گوناگون هستيم. با ورود هرچه وسيع¬تر اين تكنيك توليد به صنايع توليدي، نياز به بازرسي و تست محصولات توليد شده بر پايه اين روش نيز افزايش يافته است. از جمله اين روش¬هاي تست، تست غيرمخرب فراصوت است كه در صنايع گوناگون كاربرد وسيعي دارد. بلوك¬هاي كاليبراسيون در تست¬هاي غيرمخرب نقش كليدي ايفا مي¬كنند و به نوعي ميزان صحت تست انجام شده را تعيين مي¬¬كنند. بلوك¬هاي موجود خواص متفاوتي نسبت به قطعات توليد افزايشي دارند و همچنين وجود ناهمسانگردي در قطعات توليد افزايشي باعث بروز خطاي اندازه¬گيري قابل توجهي در تست فراصوت نمونه¬ها مي¬شود. همچنين با توجه به توانايي¬هاي فرايند توليد افزايشي، امكان توليد عيوب داخلي رپدر موقعيت معين فراهم شده است. اين قابليت منحصر به فرد، امكان تركيب بلوك¬هاي كاليبراسيون فعلي با هدف كوتاه كردن فرايند توليد و صرفه¬جويي در ماده اوليه را فراهم مي¬كند. در اين پايان¬نامه به بررسي موانع و راهكارهاي استفاده از مزاياي فرايندهاي توليد افزايشي براي توليد بلوك¬هاي كاليبراسيون تست فراصوت پرداخته شده است. چند نمونه بلو مرجع طراحي شد و يك نمونه ساخته و مورد تست قرار گرفت تا كارايي اين روش ساخت در عمل بررسي شود. در طي انجام اين پروژه شبيه¬سازي سه بعدي و دوبعدي انتشار موج فراصوت در ماده ناهمسانگرد با خواص مكانيكي تعيين شده به كمك تست تجربي غيرمخرب فراصوت، براي مطالعه اثر ناهمسانگردي در انتشار موج انجام گرفته است. يك نمونه بلوك با عيوب جانمايي شده ساخته شد و به روش¬هاي گوناگوني از جمله روش¬هاي غيرمخرب فراصوت و راديوگرافي، و روش¬هاي مخربي چون ماشينكاري با بكارگيري ميكروسكوپ نوري به بررسي دقت و صحت ساخت قطعه پرداخته شد. تست¬هاي انجام گرفته دقت و صحت ساخت عيوب جانمايي شده را تاييد كرده و قابليت بالاي فرايند ذوب انتخابي ليزري را براي ساخت بلوك¬هاي مرجع تست فراصوت تصديق مي¬كند.

1398/03/01

The Design and Manufacturing of Calibration Blocks for Nondestructive Testing by means of Additive Manufacturing

3/2/2019 12:00:00 AM

Calibration blocks play a vital role in nondestructive testing (NDT) of mechanical parts. Calibration blocks are parts with known specifications and characteristics which are used to verify testing equipment. Ultrasonic testing (UT) is one of the most common Nondestructive Testing methods were used for inspection and evaluation of metallic and composite parts. Manufacturing of calibration blocks for UT testing has a strong background in the past few decades, however, they haven’t experienced significant changes since then due to limitations in manufacturing processes. Additive manufacturing (AM), also known as 3D Printing, open up a new way of fabricating parts layer-by-layer in oppose to conventional (subtractive) manufacturing processes. With the aid of AM-based processes, parts with any level of complexity in geometry could be built directly from CAD models. As a consequence, the calibration block industry could obtain benefits from this huge development and blocks with artificial embedded defects with known geometry and coordinates could be built in order to make better representatives of real flaws. In this thesis, the possibility of manufacturing calibration blocks by means of AM processes were investigated in detail, along with the proposition of innovative designs and their superiorities for the future calibration blocks. To this goal, first, definitions and scientific background of AM processes and parameters, as well as ultrasonic testing were fully addressed. Then, an extensive review in the literature were carried out. In the next step, calibration block manufacturing procedure and specification standards were studied. Simultaneously, several factors were addressed and investigated to evaluate the habilitation of additive manufactured parts, especially selective laser melted (SLM) parts, to be replaced with conventional blocks. Finally, one of the proposed blocks with some embedded features, which are played as simulated internal defects, were fabricated by means of SLM process and evaluated via A-scan ultrasonic testing and radiography testing (RT), along with machining of mentioned part for light optical microscopy (LOM) observation as destructive testing. The result of each test discussed in detail and compared to the others. With regard to anisotropic microstructure of SLM parts, several simulations were done to study ultrasound wave propagation in an anisotropic media to predict wave behavior and reflections in such cases, as well as to understand the mechanism of ultrasonic testing. Mechanical properties of fabricated SLM sample were determined via pulse-echo ultrasonic testing to feed into finite element software in order to obtain more reliable results. Simulations were carried out in two ways, 3D and 2D, for both normal and transverse wave propagation via ABAQUS/CAE software. Results for defective and healthy parts for isotropic and anisotropic structures were compared and justified. Throughout the simulations, concepts of infinite elements and phased array ultrasonic wave propagation and some MATLAB programming were used. In the final section, the results from numerical simulations were approved by test results.