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مقاله جوشكاري Effects of welding parameters on the characteristics of magnesium alloy joint welded by resistance spot welding with cover plates

مقاله جوشكاري با عنوان : Effects of welding parameters on the characteristics of magnesium alloy joint welded by resistance spot welding with cover plates

Hongxin Shi a,b,*, Ranfeng Qiu a, Jinhong Zhu a, Keke Zhang a, Hua Yu a, Gaojian Ding

چكيده :

Magnesium alloy AZ31B sheets were welded using the technique of resistance spot welding with cover
plates. The effects of welding parameters on the characteristics of the joint were investigated. The joint
with larger nugget and higher tensile shear load was obtained under relatively low welding current condition.
Enhancing electrode force and extending down-sloping time are effective for inhibiting pores formation
and increasing the tensile shear strength of the joint under corresponding welding conditions.
The results reveal that the technique is feasible to weld magnesium alloy.

مقاله جوشكاري Electrical contact resistance effect on resistance spot welding

مقاله جوشكاري با عنوان : Electrical contact resistance effect on resistance spot welding

P.S. Wei a,., T.H. Wub

چكيده :

The effects of local electrical contact resistance on transport variables, cooling rate, solute distribution,
and nugget shape after solidification responsible for microstructure of the fusion zone during resistance
spot welding are realistically and systematically investigated. The model accounts for electromagnetic
force, heat generation and contact resistances at the faying surface and electrode–workpiece interfaces
and bulk resistance in workpieces. Contact resistances are composed of film and constriction resistances,
as functions of hardness, temperature, electrode force and surface condition. The computed results show
that the bulk dynamic electrical resistance cannot reliably reflect transport processes and nugget shape,
unless the local constriction resistance and electric current density are known. Regardless of high film
resistance, nugget growth and transport processes are independent of film resistance due to delayed
response time of local electric current in the early stage. A decrease in constriction resistance, however,
delays nugget formation, enhances convection and solute mixing, and changes circulation direction of the
stronger convection cell during cooling period.

مقاله جوشكاري Effects of Welding Parameters and Surface Pretreatments on Resistance Spot Welding of AZ31B Mg Alloy

مقاله جوشكاري با عنوان :

Effects of Welding Parameters and Surface Pretreatments on Resistance
Spot Welding of AZ31B Mg Alloy

Shiquan Zhou1, Lei Liu2,3, Jae Pil Jung4,*, Mok-Young Lee5, and Y. Norman Zhou3

چكيده :

The resistance spot weldability of AZ31B magnesium alloy using AC (alternating current) was investigated
in this paper. The surfaces of sheet coupons were prepared by acetone cleaning (as-received) and some coupons
were also cleaned with chromic acid (H2Cr2O7) after acetone cleaning (acid-cleaned). The surfaces of the
as-received AZ31B sheets consisted of MgO, Mg(OH)2, and MgCO3. The extent and thickness of the surface
oxide/reaction layer of the sheets varied according to the fabrication process of the sheets, and resulted in
different contact resistance. Effects of welding current and weld time were investigated while the electrode
force was kept constant. The results indicated that the as-received sheets produced expulsion both at the
faying surface and at the work piece/electrode interface due to high contact resistance. Diluted chromic acid
cleaning reduced contact resistance and produced good weld quality. Increasing the welding current and weld
time enhanced not only the nugget size and joint strength, but also increased indentation on the weld surfaces.
A weld lobe was established considering the minimum joint strength, weld expulsion, and surface indentation
based on a relevant American Welding Society Standard.

ختومات علوم غريبه(نقشبندي)

اين كتاب براي آن دسته از كساني است كه به علوم ماوراء الطبيعه علاقه مندند. توجه اكيد شود كه دستورات اين كتاب در راههاي خلاف و ضايع كردن حق مردم مورد استفاده قرار نگيرد كه گناه آن متوجه شخص خاطي خواهد بود

طلسمات نقشبندي و دعاهاي قرآني

اين كتاب براي علاقمندان به علوم ماوراء الطبيعه و علوم قرآني تهيه شده است. توجه اكيد شود از مطالب اين كتاب در جهت خلاف شرع استفاده نشود كه گناه آن متوجه شخص خاطي خواهد بود...

فايل كامل دوره اصول و قواعد طراحي پايپينگ آموزشگاه نوين پارسيان تهران

فايل كامل دوره اصول و قواعد طراحي پايپينگ (piping)نوين پارسيان در قالبpdf (كل 10 جلسه)

شامل:

آشنائي با مهندسي و روند انجام پروژه ها ووظايف و نحوه ارتباط،مدارك،استانداردها وكدهاي طراحي درپرو‍ژ ه هاي نفت و گاز ،پالايش و پتروشيمي و نيروگاه و واحد صنعتي

شنايي با روند انجام پروژه
طراحي فرآيند و مدارك مربوطه
آشنايي با PIPING و استانداردها وكدهاي مربوطه
Plot plan design (نحوه طراحي واحد)
آشنايي با تجهيزات ثابت و دوار و نحوه طراحي آنها
آشنايي با ابزار دقيق و مدارك مربوطه
محاسبات هيدروليكي و ....

بتن غلتكي - سد

كتاب گام به گام روش اجراي سد به روش بتن غلتكي از صفر تا صد. اين كتاب گزينه مناسبي براي مهندسان عمران و رشته آب است كه در اين پروژه ها حضور نداشته اند. با مطالعه دقيق اين كتاب نگران استخدام خود در اين پروژها نباشيد.

فرآيند توليد پروپيلن گليكول و طراحي آن با نرم افزار HYSYS

فرآيند توليد پروپيلن گليكول

و طراحي آن با نرم افزارHYSYS

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مدلسازي و بهينه سازي پويا از پروپان حرارتي فعال براي توليد اتيلن

مقاله عنوان مدلسازي و بهينه سازي پويا از پروپان حرارتي فعال براي توليد اتيلن به زبان انگليسي در زير آماده شده است.تحت اين مقاله با قيمتي كمتز نسبت به سايت هاي معتبر علمي همچون ساينس دايركت و Elsevier در اختيار شما قرار گرفته است.

a b s t r a c t
In tubular reactors inside a cracking furnace, heat transfer, thermal cracking reactions and coke buildup
take place and closely interact with each other. It is important to understand the process and optimize
its operation. A 1-dimensional (1D) pseudo-dynamic model was developed based on first principle and
implemented in gPROMS®. Coke buildup inside the tube wall was also accounted for. The model was
validated dynamically. The impact of process gas temperature profile, and constant tube outer wall temperature
profile on product yields and coking rate are assessed. Finally, dynamic optimization was applied
to the operation of this tubular reactor. The effects of coking on reduction of production time and the
decoking غير مجاز مي باشدt have been considered. The tube outer wall temperature profile and steam to propane ratio
in the feed were used as optimization variables. Dynamic optimization investigation indicates that it can
improve operating profit by 13.1%.

جزوه درسي موازنه انرژي و مواد (دكتر پرويني)

جزوه درسي موازنه انرژي و مواد تاليف دكتر پرويني در 93 صفحه در قالب يك فايل pdf در زير ارائه شده است. اين جزوه شامل تمام سرفصل هاي درس موازنه انرژي و مواد بهمراه مثال ها و نمونه سوالات متعدد است كه مطالعه آن در درك مطلب و تسلط بسيار موثر بوده و شما را براي امتحانات پيشرو آماده مي كند.