Eulerian FEA With Volume of Solid (VOS) Application in Metal Forming

The adaptation of the volume of fluid method (VOF) to solid mechanics (VOS) is presented in this work with the focus on metal forming applications. The method is discussed for a general non-uniform mesh with Eulerian finite element formulation. The implementation of the VOS method in metal forming applications is presented by focusing on topics such as the contact between the tool and the workpiece, tracking of the free surface of the material flow and the connectivity of the free surface during the whole process. Improvement on the connectivity of the free surface and the representation of curves is achieved by considering the mechanics of different metal forming processes. Different applications are simulated and discussed to highlight the capability of the VOS method.

Beam-Like Major Compliant Joint Methodology for Automotive Body Structures

One of major difficulties in developing and employing a concept model of a vehicle is to develop a simple and accurate model of joints. A vehicle joint is a subassembly formed by several members that intersect together. It is a thin-walled structure formed by overlapping metal sheets fastened by spot welds. The study of the joints has been important, because they can deform locally. This flexibility can affect noise, vibration and harshness (NVH) characteristics of a vehicle plus other structural performance characteristics under different loading conditions. The main difference between various kinds of concept models is the representation of body joints. Joints are important components of the auto body because they affect significantly, and in some cases, they even dominate, the static and dynamic behavior of a model. This paper introduces a new beam-like major compliant joint methodology. Joints are simulated with different parametric representations that present the major differences among various concept models. The development procedure of the beam-like major compliant joint is explained and the benefits of using this representation are discussed.

Experimental Determination of Parameters to Avoid Arcing in Electrical Discharge Machining of Titanium Diboride Particulate Reinforced Ferrous Matrix Composite

Titanium diboride (TiB2) particles are most popular reinforcement along with tungsten carbide for ferrous matrices for developing composites with high specific modulus, improved wear resistance and hardness while providing good fatigue properties as well. The hardness of such composites poses a problem in conventional machining in terms of very fast wear rates of tools and very high cutting forces. Non-conventional processes like electrical discharge machining (EDM) are very popular for machining of conductive composites like TiB2 reinforced ferrous matrix composites. However, there are a large number of process parameters for EDM which need to be selected and controlled carefully for satisfactory machining performance. Parameter settings which lead to arcing are specifically investigated and avoided as this phenomenon leads to uncontrolled machining through short circuit conditions and large energy discharges. In this paper, an experimental approach to determine the parameter settings which will lead to arcing during EDM machining of TiB2 particulate reinforced ferrous matrix composite is discussed. Values of major EDM process parameters are selected in roughing, intermediate and finishing domains. Experimental trials using L27 design of experiment are conducted and parameter combinations leading to arcing are recorded and the zone of parameters that can lead to arcing is identified.

Design and Testing of Innovative Rotational Mould Heated by Thermal Fluid

Rotomoulded plastic parts have no internal stresses, as it is a process carried out at lower temperatures than injection moulding and no pressure is applied. The main disadvantage is the high cycle times needed. This paper focuses on reducing this cycle time and in producing a mould using standardized parts. For cycle time reducing, it is proposed to heat the mould by thermal fluid in continuous circulation; heat transfer processes have been studied for over 20 different configurations of the oil’s inlet – outlet, obtaining acceptable results with a manifold with 25 perforations in the front and rear faces. This configuration has been optimized by computational fluids dynamics, allowing reducing heating and cooling time and improving the energetic efficiency and the uniformity of heating. Design, simulations and testing of a 100 mm3 cube have been carried out in order to produce a standardized mould; this mould consists in some standardized parts and a nickel shell, obtained by rapid prototyping and electroforming process. This shell can be removed from the rest of elements in the mould, allowing thus to obtain parts with any other geometry just by changing the nickel shell. An experimental machine for testing has been developed as well.

Comparison of Motion Characteristics of High Performance CNC Rotary Tables

In this paper, the motion performances of the two rotary tables which are driven by roller gear cam and direct drive motor are measured and compared. The table with roller gear cam was controlled in semi-closed loop and full-closed loop methods while the other was controlled only in full-closed loop method. In the measurements, the positioning accuracy and repeatability, rotational fluctuation, frequency response, step response and etc of the systems were measured. All these tests were carried out without any kind of compensation methods such as pitch error or cogging torque compensation etc. Three rotary encoders for rotary table with roller gear cam and one rotary encoder for rotary table with direct drive motor were used for measurements. Furthermore, the simulations were carried out by mathematical models and the results were compared with measured results. The comparison shows that the measured and simulated results have a good agreement. From the simulation results, the friction torque was identified and also compared. The results imply that though both the tables show high performances, the performances of the rotary table driven by roller gear cam are comparatively higher than that of rotary table driven by direct drive motor.

Innovative Design of Lightweight on Board Hydrogen Storage Tank

The hydrogen economy envisioned in the future requires safe and efficient means of storing hydrogen fuel for either use onboard vehicles, delivery on mobile transportation systems or high-volume storage in stationary systems. The main emphasis of this work is placed on the high -pressure storing of gaseous hydrogen on-board vehicles. As a result of its very low density, hydrogen gas has to be stored under very high pressure, ranging from 350 to 700 bars for current systems, in order to achieve practical levels of energy density in terms of the amount of energy that can be stored in a tank of a given volume. This paper presents 3D finite element analysis performed for a composite cylindrical tank made of 6061-aluminum liner overwrapped with carbon fibers subjected to a burst internal pressure of 1610 bars. As the service pressure expected in these tanks is 700 bars, a factor of safety of 2.3 is kept the same for all designs. The results indicated that a stress reduction could be achieved by a geometry change only, which could increase the amount of pressure sustained inside the vessel and ultimately increase the amount of hydrogen stored per volume. Such reductions in the stresses will decrease the thickness dimension required to achieve a particular factor of safety in a direct comparison to a cylindrical design.

Optimal Viscous Damper Placement Using Level Set Topology Optimization Method

Vibration control has always been of great interest for many researchers in different fields, especially mechanical and civil engineering. One of the key elements in control of vibration is damper. One way of optimally suppressing unwanted vibrations is to find the best locations of the dampers in the structure, such that the highest dampening effect is achieved. This paper proposes a new approach that turns the conventional discrete optimization problem of optimal damper placement to a continuous topology optimization. In fact, instead of considering a few dampers and run the discrete optimization problem to find their best locations, the whole structure is considered to be connected to infinite numbers of dampers and level set topology optimization will be performed to determine the optimal damping set, while certain number of dampers are used, and the minimum energy for the system is achieved. This method has a few major advantages over the conventional methods, and can handle damper placement problem for complicated structures (systems) more accurately. The results, obtained in this research are very promising and show the capability of this method in finding the best damper location is structures.

Strength Evaluation and Failure Prediction of a Composite Wind Turbine Blade Using Finite Element Analysis

Strength evaluation and failure prediction on a modern composite wind turbine blade have been conducted using finite element analysis. A 3-dimensional finite element model has been developed. Stresses and deflections in the blade under extreme storm conditions have been investigated for different materials. The conventional wood design turbine blade has been compared with the advanced E-glass fiber and Carbon epoxy composite blades. Strength has been analyzed and compared for blades with different laminated layer stacking sequences and fiber orientations for a composite material. Safety design and failure prediction have been conducted based on the different failure criteria. The simulation error estimation has been evaluated. Simulation results have shown that finite element analysis is crucial for designing and optimizing composite wind turbine blades.

Analysis of Geometric Characteristics of Scroll Compression Chamber for Scroll Fluid Machine

Based on the general geometrical model of scroll compression chamber for scroll fluid machine, the geometric characteristics of scroll compression chamber, such as width, length, volume, and comprehensive curvature radius at the mesh point, and their variation as well are comprehensively analyzed. It is shown by the analysis that among all of the geometric characteristics, the width variation is the most complicated one; the comprehensive variation of the width together with the length can be used to determine the deformation processes of the chamber. The variability of its length, volume, and comprehensive curvature radius at meshing points should be taken as its basic deformation characteristics. For a scroll compression chamber with involute of circle, its deformation efficiency is higher and dynamic stability is excellent. At the same time, the scroll wrap with involute of circle is easy to fabricate and the profile with involute of circle is used widely for the major part of the scroll profile.

Nested Ripple Down Rules (NRDR) as a Design Assistant in Mechanical Dimensional Tolerancing

The dimensional tolerancing knowledge management system presented in this paper uses Nested Ripple down Rules (NRDR) targeted towards incrementally capturing expert design knowledge. A demonstrated example of such captured knowledge is that which human designers utilize in order to specify dimensional tolerances on shafts and mating holes in order to meet desired classes of fit as set by relevant engineering standards. In doing so, NRDR interface was designed to receive mathematical functions with their specifications prior and during the KA process. This is necessary to be able to exploit relationships among several classes with respect to certain numerical features of the cases in order to accelerate the convergence of the NRDR knowledge acquisition process by generating artificial cases which are likely to trigger the addition of exception rules. The incorporation of equations constitutes a novel contribution to the field of knowledge acquisition with NRDR. The developed dimensional tolerancing knowledge management system would help mechanical designers become more effective in the time-consuming tolerancing process of their designs in the future.