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Showing posts from November, 2020

### Design Procedure Review – 02, Transverse Fillet Weld by Kotur Raghavan

General It would be hard to come across structures and mechanical assemblies which do not contain welded connections. However, in almost all the stress analysis tasks using FEA the weld geometries are not explicitly accounted for. Components which are welded together are assumed to be rigidly connected. One of reasons is the challenges involved because of geometric complexities. Moreover, welded connections are normally configured based on industry standards. All the same, we find chapters on design of welds in all books of structural and mechanical design. One such problem is taken up for study in the present article. This is the second in the DPR series of articles. Transverse Fillet Weld The configuration taken up for study is shown in Fig. 1 below. Load transfer takes place between the plate 1 and plates 2 through the welds 3. Fig. 1 The present study is in the context of the design procedure described by Shigley and Minschke in their book Mechanical Engineering Desig

### Saint-Venant’s Principle, Interpretations and Applications by Kotur Raghavan

General Adhemar Jean Claude Barre de Saint-Venant, better known as Saint-Venant, was a nineteenth century Mechanician and Mathematician. He has made pioneering contributions in the areas of fluid Mechanics and Theory of Elasticity. Fig. 1 In solid mechanics he is best remembered for development of mathematical equations applicable to torsion and the Saint-Venant’s Principle which deals with treatment of statically equivalent forces. This article is essentially concerned with Saint-Venant’s Principle, interpretations and applications. The Principle If the forces acting on a small portion of the surface of an elastic body are replaced by another statically equivalent system of forces acting on the same portion of the surface, this redistribution of loading produces substantial changes in the stresses locally but has a negligible effect on the stresses at distances which are large in comparison with the linear dimensions of the surface over which the forces are acting. There

### HOMEPAGE

Introduction    https://www.fembestpractices.com/2020/09/general-opener.html BASICS 1.        Methods of Structural Analysis 2.        Load paths in human body 3.        Load paths in a bicycle 4.        Human Body, More insights, Pain and stress 5.        Components in series / parallel - 1 6.        Components in series/parallel - 2 1.        Consistent units in FEA Minimum Constraints 1.        Overview 2.        Application: Sanity Checks 3.        Application: Zero resultant force problems 4.        Application: Inertia Relief Submodeling Two-Dimensional Elements 1.        Plane stress, Plane strain and Generalized plane strain 2.        2D elements – example Problem Tower Bolts 1.        Design analysis – simple model 2.        Review of assumptions 3.        Nonlinear model with tension-only links General 1.        Verification and Validation 1.        Saint-Venant Principle – Interpretations and Applications FEA and Design 1.

### Design Procedure Assessment, DPA-01, Square Keys by Kotur Raghavan

General Keys are among the simplest mechanical elements. They are deployed to transmit power (torque) from a shaft to a hub or vice versa. The hubs are normally an itegral part of a bigger component such as a pulley, gearwheel or a turbine disk. The figure below is representative of the functioning of keys. Fig. 1 The applied torque from hub to the shaft or the other way is entirely transmitted through the key by way of contacts. There are four contact surfaces on the side flanks of the key. Two of them are active depending on the mode of power transmission and also the direction of rotation. In addition, the top and bottom surfaces also may come into play because the key normally has snug fit with the other two components. Traditional Design Approach In the figure below, free body diagrams of the key is shown. They correspond to the case of power transmission from the hub to the shaft in the anti-clockwise direction or from the shaft to the hub in the clockwise direction. Th

### V and V in Structural Analysis by Kotur Raghavan

In many engineering and software activities a frequently used phrase is “verification and Validation (V and V)”. One can find a large number of articles addressing this topic. The articles focus on the essential differences between the two entities. The field of structural analysis along with finite element analysis is no exception. Considerable work has been done by NAFEMS in collaboration with ASME and many of the published work is available in the open literature. Interested readers can refer those articles for in-depth information. Fig. 1 In this brief article, the essential aspects of V and V in the context of structural analysis and FEA are presented based on the information available in these publications. o    The most fundamental fact in the present context is that one verifies a CODE, whereas simulation models are validated.   o    The codes, like ANSYS and ABAQUS, are developed for facilitating simulation of practical structural analysis problems. The codes thus d

### Traditional Design Teaching – Chief Concerns by Kotur Raghavan

Design Approaches Broadly there are two classes of approaches to Engineering Design. The first is the traditional approach. In this approach the designs are arrived at using the information available in Codes, Standards and Handbooks. Industrial equipment like boilers and civil engineering structures like bridges, transmission towers and buildings are designed using this approach. As an example, we can quote the ASME’s Boiler and Pressure Vessel Code, Section VIII, Division One . Whereas the codes and standards yield satisfactory designs, the main objection will be that they are often too conservative and the designs tend to be unnecessarily bulky and heavy. For simpler designs the traditional method involves the use of formulae from Applied Mechanics and Strength of Materials. Most of the Machine Design books use this as basis. The approach is useful for simple mechanical components like shafts, pulleys and springs. There are limitations and shortcomings in this approach which will

### FEA and Design, An Overview by Kotur Raghavan

In the year 1956, Professor Ray Clough and his associates at the University of Berkley published their work leading to the development of the Constant Strain Triangle (CST) element. That was the first ever element developed for continuum (2D plane stress in that case). Many consider the CST to be the mother of all finite elements. It will not be wrong to consider the year 1956 to be the birth year of the modern finite element method as is known today to all CAE practitioners. We can say that FEA is more than sixty years old today. The impact of the finite element method can hardly be over-emphasized. The method has taken the field of structural analysis to heights which were never known before. This is due to the progress theory, solution algorithms and growth in computational technology. An added catalytic aspect has been the availability of ready-to-use analysis packages which cater to almost all structural analysis requirements. In today’s scenario no structural analysis problem i