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Abstrak :
Resistance spot welding (RSW) merupakan metode pengelasan yang sudah banyak digunakan dalam dunia industri terutama industri otomotif. RSW menggabungkan dua pelat metal menggunakan panas yang berasal dari arus elektrik. Untuk mengurangi biaya yang digunakan untuk melakukan eksperimen secara langsung, simulasi RSW mulai dikembangkan. Simulasi RSW membutuhkan Initial Value dari electric contact resistance yang terdapat pada RSW. Penelitian ini bertujuan untuk mencari Initial Value tersebut agar simulasi dapat dilaksanakan. Initial value yang ditemukan akan digunakan untuk simulasi selanjutnya. Penelitian dilakukan menggunakan eksperimen dan juga simulasi untuk dapat membandingkan hasil dari dua metode tersebut. Pada eksperimen RSW, parameter yang divariasikan adalah cycle time. Cycle Time divariasikan sebanyak 1, 2, 3, 4, 5, 6, 7, 8, 9, dan 10 . Pada simulasi RSW, parameter yang divariasikan adalah waktu pengelasan yaitu selama 20ms, 40ms, 60ms, 80ms, 100ms, 120ms, 140ms, 160ms, 180ms, dan 200ms. Hasil las berupa ukuran nugget dari dua metode tersebut akan dibandingkan. Perbandingan hasil menunjukkan bahwa simulasi dengan initial value 200 memiliki ukuran nugget yang paling mendekati rata-rata ukuran nugget eksperimen. ......Resistance spot welding (RSW) is a commonly used welding method in industry, especially in automotive industry. RSW joins two metal plates using heat generated from electric current. To reduce the experiment cost, RSW simulation developed. RSW simulation needs Initial Value from electric contact resistance that consists on RSW. This research is conducted to find the initial value needed for RSW simulation. The initial value will be used for the next simulation Both experiments and simulations will be conducted in this research to compare the results. In RSW experiment, the variated parameter is cycle Time. The cycle time is variated as 1, 2, 3, 4, 5, 6, 7, 8, 9, dan 10. In RSW simulation, the variated parameter is welding Time as 20ms, 40ms, 60ms, 80ms, 100ms, 120ms, 140ms, 160ms, 180ms, and 200ms. The welding result of the nugget size of the two methods above will be compared. Comparison results show that simulation with initial value of 200 has the closest nugget diameter result with experiment.

Abstrak :

Resistance Spot Welding (RSW) adalah salah satu metode pengelasan yang meleburkan metal itu sendiri menggunakan arus listrik serta tekanan pneumatik. RSW sangat sering dijumpai di berbagai industri terutama industri otomotif dan industri dirgantara dimana diperlukan kecepatan untuk las titik serta temperatur yang terpusat. Elektroda dari tembaga biasanya adalah pilihan utama sebagai sumber penyalur arus listrik dan penekan. Bentuk dari elektroda itu sendiri berpengaruh atas ukuran nugget yang tercipta. Investigasi kali ini mencari dampak perubahan sudut elektroda terhadap besar nugget dengan memvariasikan bentuk elektroda dengan sudut kemiringan 30°, 45â?°, 60° terhadap benda kerja, serta bentuk Lab DTM. Nilai dari initial value contact resitance adalah 230 dengan menggunakan simulasi dari perangkat lunak ANSYS. Ditemukan hubungan bahwa semakin besar sudut elektroda terhadap benda kerja (semakin lancip elektroda) maka semakin besar juga diameter nugget yang tercipta. Hal ini dikarenakan ukuran elektroda yang mengecil sehingga current density dapat menjadi lebih terpusat. Hasil ini secara konsisten ditunjukan dengan berbagai variasi initial value. Didapati juga bahwa semakin besar initial value contact resistance, maka semakin besar juga diameter nugget.

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Resistance spot welding (RSW) is one of a few method of welding which melt its own metal using electric current and pneumatic pressure. RSW often found in various industry especially in otomotif industry and aeroplane industry where speed and temperatur distribution is really needed. Electrode made from copper usually is the main option for source of electric conductor and pressure. Shape of electrode itself affect the nugget size of the weld. This investigation will found the effect of changing the angle of attack of electrode for the weld nugget size with varying the angle from 30â?°, 45°, 60â?°, and DTM lab electrode. Value from initial value contact resistance will also be 230 using simulation with ANSYS APDL software. It was found that the bigger the angle (more pointed) electrode will produce a bigger weld nugget diameter. This is because of the electrode size getting smaller therefore creating a more focused current density resulting in bigger nugget weld. This result is consistent eventhough the initial value was changed. It was also found that the higher the inital value contact resistance, the nugget diameter would also got bigger.

Abstrak :
Many physical problems are most naturally described by systems of differential and algebraic equations. This book describes some of the places where differential-algebraic equations (DAE's) occur. The basic mathematical theory for these equations is developed and numerical methods are presented and analyzed. Examples drawn from a variety of applications are used to motivate and illustrate the concepts and techniques. This classic edition, originally published in 1989, is the only general DAE book available. It not only develops guidelines for choosing different numerical methods, it is the first book to discuss DAE codes, including the popular DASSL code. An extensive discussion of backward differentiation formulas details why they have emerged as the most popular and best understood class of linear multistep methods for general DAE's. New to this edition is a chapter that brings the discussion of DAE software up to date. The objective of this monograph is to advance and consolidate the existing research results for the numerical solution of DAE's. The authors present results on the analysis of numerical methods, and also show how these results are relevant for the solution of problems from applications. They develop guidelines for problem formulation and effective use of the available mathematical software and provide extensive references for further study.

Abstrak :
Researchers and graduate students in applied mathematics and engineering will find Initial-Boundary Value Problems and the Navier-Stokes Equations invaluable. The subjects addressed in the book, such as the well-posedness of initial-boundary value problems, are of frequent interest when PDEs are used in modeling or when they are solved numerically. The book explains the principles of these subjects. The reader will learn what well-posedness or ill-posedness means and how it can be demonstrated for concrete problems. There are many new results, in particular on the Navier-Stokes equations. When the book was written, the main intent was to write a text on initial-boundary value problems that was accessible to a rather wide audience. Therefore, functional analytical prerequisites were kept to a minimum or were developed in the book. Boundary conditions are analyzed without first proving trace theorems, and similar simplications have been used throughout. The direct approach to the subject still gives a valuable introduction to an important area of applied analysis.

Abstrak :
This monograph presents teaching material in the field of differential equations while addressing applications and topics in electrical and biomedical engineering primarily. The book contains problems with varying levels of difficulty, including Matlab simulations. The target audience comprises advanced undergraduate and graduate students as well as lecturers, but the book may also be beneficial for practicing engineers alike.

Abstrak :
This textbook provides a step-by-step approach to numerical methods in engineering modelling. The authors provide a consistent treatment of the topic, from the ground up, to reinforce for students that numerical methods are a set of mathematical modelling tools which allow engineers to represent real-world systems and compute features of these systems with a predictable error rate. Each method presented addresses a specific type of problem, namely root-finding, optimization, integral, derivative, initial value problem, or boundary value problem, and each one encompasses a set of algorithms to solve the problem given some information and to a known error bound. The authors demonstrate that after developing a proper model and understanding of the engineering situation they are working on, engineers can break down a model into a set of specific mathematical problems, and then implement the appropriate numerical methods to solve these problems.