Design of Robust Mechatronics Embedded Systems by Integration of Virtual Simulation and Mechatronics Platform

Increasing demands on the productivity of complex systems, such as machine tools and their steadily growing technological importance will require the application of new methods in the product development process. This paper shows that the analysis of the simulation results from the simulation based mechatronic model of a complex system followed by a procedure that allows a better understanding of the dynamic behavior and interactions of the components. Mechatronics is a design philosophy, which is an integrating approach to engineering design. Through a mechanism of simulating interdisciplinary ideas and techniques, mechatronics provides ideal conditions to raise the synergy, thereby providing a catalytic effect for the new solutions to technically complex situations. This paper shows how the mechatronic products can exhibit performance characteristics that were previously difficult to achieve without the synergistic combination. The paper further examines an approach used in modeling, simulation and optimization of dynamic machine tools and adopts it for general optimized design of mechatronics instrumentation and portable products. By considering the machine tool as a complete mechatronic system, which can be broken down into subsystems, forms the fundamental basis for the procedure. Starting from this point of view it is necessary to establish appropriate simulation models, which are capable of representing the relevant properties of the subsystems and the dynamic interactions between the machine components. Many real-world systems can be modeled by the mass-spring-damper system and hence considering one such system, namely Mechatronics Technology Demonstrator (MTD) is discussed here. MTD is a portable low cost, technology demonstrator, developed and refined by the authors. It is suitable for studying the key elements of mechatronic systems including; mechanical system dynamics, sensors, actuators, computer interfacing, and application development. An important characteristic of mechatronic devices and systems is their built-in intelligence that results through a combination of precision, mechanical and electrical engineering, and real time programming integrated to the design process. The synergy can be generated by the right combination of parameters, that is, the final product can be better than just the sum of its parts. The paper highlights design optimization of several mechatronic products using the procedures derived by the use of mass spring damper based mechatronic system. The paper shows step by step development of a mechatronic product and the use of embedded software for portability of hand held equipment. A LabVIEW based platform was used as a control tool to control the MTD, perform data acquisition, post-processing, and optimization. In addition to the use of LabVIEW software, the use of embedded control system has been proposed for real-time control and optimization of the mass-spring-damper system. Integrating embedded control system with the mass-spring-damper system makes the MTD a multi-concepts Mechatronics platform. This allows interface with external sensors and actuators with closed-loop control and real-time monitoring of the physical system. This teaches students the skill set required for embedded control: design control algorithms (model-based embedded control software development, signal processing, communications), Computer Software (real-time computation, multitasking, interrupts), Computer hardware (interfacing, peripherals, memory constraints), and System Performance Optimization. This approach of deriving a mathematical model of system to be controlled, developing simulation model of the system, and using embedded control for rapid prototyping and optimization, will practically speed product development and improve productivity of complex systems.

Modeling Phase Transformation Kinetics and Their Effect on Hardness and Hardness Depth in Laser Hardening of Hypoeutectoid Steel

Much research has been done to model laser hardening phase transformation kinetics. In that research, assumptions are made about the austenization of the steel that does not translate into accurate hardness depth calculations. The purpose of this paper is to develop an analytical method to accurately model laser hardening phase transformation kinetics of hypoeutectoid steel, accounting for non-homogeneous austenization. The modeling is split into two sections. The first models the transient thermal analysis to obtain temperature time-histories for each point in the workpiece. The second models non-homogeneous austenization and utilizes continuous cooling curves to predict microstructure and hardness. Non-homogeneous austenization plays a significant role in the hardness and hardness depth in the steel. A finite element based three-dimensional thermal analysis in ANSYS is performed to obtain the temperature history on three steel workpieces for laser hardening process with no melting; AISI 1030, 1040 and 1045 steels. This is followed by the determination of microstructural changes due to ferrite and pearlite transformation to austenite during heating and the subsequent austenite to martensite and other diffusional transformations during cooling. Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation is used to track the phase transformations during heating, including the effects of non-homogenous austenitization. The solid state nodal phase transformations during cooling are monitored on the material’s digitized Continuous Cooling Transformation (CCT) curve through a user defined input file in ANSYS for all cooling rates within the Heat Affected Zone (HAZ). Material non-linearity is included in the model by including temperature dependent thermal properties for the material. The model predictions for hardness underneath the laser and the HAZ match well with the experimental results published in literature.

Avoiding of Self-Loosening in Components With Multiple Screw Joints

Self-loosening of fastened systems is known as a severe damage mechanism besides the loss of preload due to relaxation and as a result of this the failure of the joint. Main problem is, that self-loosening mostly leads to a rapid preload loss when occurs. In the 1970s first systematic investigations due to this are reported from Junker et al. using a transverse-vibrational test stand [13]. Nowadays numeric calculation approaches are available (e.g. [12]). All approaches show that very small displacements from loading before complete sliding are sufficient to induce self-loosening — which is a screw rotation against its tightening direction without material rupture of the screw. Today the mechanism of self-loosening under uni-axial transverse load of single-screwed joints with plain bearing surface is understood and predictable. Also combined loads of vibration and rotation became the focus of university-based research. The challenge is to transfer the knowledge about the mechanism to component fastened systems with multi-screw joints. The fundamental mechanism is not sufficient for component design. This is the reason why up to now no prediction in advance is established in guidelines. First, this paper shows the time-sequence of self-loosening in general with its different stages. The second step is to work out important influences on self-loosening which will be shown by existing calculations. Then a stress-based calculation and a better criterion for self-loosening will be developed. Next step, if analytics come to their limits, is the numeric simulation of system behavior. With this the critical preload for self-loosening must be determined to ensure safety of the connection. Following from this screw joints can be dimensioned without risk of self-loosening. The simulation procedure includes right modelling with boundary conditions as well as defining evaluation procedure for a ‘self-loosening-safety-margin’. With simulation of a single-screw joint it gets clear that either analytical or numerical approach can be used. But already for two screws in a fastened system the limits of known equations become obvious. Finally, results of a vibrational test are shown before conclusions and outlook.

Development of Metal Matrix Nanocomposites of AA6061 – SiCp Using Ultrasonic Cavitations in Squeeze Casting Process

In the recent days, aerospace, automotive and defense sectors have been the main driving force behind the search of lighter and stronger materials in order to use in the production of vehicles. The growing demand for the production of light weight structural components and systems is fulfilled by the development of innovative metallic materials such as composites and alloys particularly based on aluminium because of their desirable properties such as low density, good castability, excellent strength and excellent corrosion resistance. Widely employed processes such as gravity and pressure die casting are used for processing aluminium alloys but the components exhibit several casting defects such as porosity, cracks, segregation and hot tears etc. This drives the industries to develop new processes which produce defect free components in shorter time as they have been under competitive pressure. Of the many such processes, squeeze casting has good capacity to produce less defective components. Squeeze casting is the process in which the molten metal solidifies under the application of pressure. The development of Aluminium Matrix Composites (AMCs) through squeeze casting has been one of the major areas of research in recent times. Research works on AMCs reinforced with micrometric particles have shown that the ability to strengthen the matrix alloy by them is lesser than nanometric particles. Metal matrices reinforced with nanoparticles are characterized by significant improvement in strength and wear resistance, improved ductility and improved dimensional stability at elevated temperatures. But, nanosized ceramic particles constitute problems during fabrication as it is extremely difficult to obtain uniform dispersion of nanoparticles in liquid metals owing to their high viscosity, poor wettability in the metal matrix, and a large surface-to-volume ratio. These problems induce agglomeration and clustering of nanoparticles. The nanoparticles can be dispersed uniformly in the metal matrix by means of employing ultrasonic cavitations. Ultrasonic cavitations include the formation, growth and collapse of micro-bubbles in liquids, under cyclic high intensity ultrasonic waves. The cavitation bubbles collapse and generate a huge amount of energy, which could be used in dispersion of the nanoparticles more uniformly in the melt. In this study, squeeze casting is combined with ultrasonic cavitations to develop Metal Matrix Nanocomposites (MMNCs) of AA6061 – SiCp as a maiden attempt. The impact of varying volume percentage of SiCp nanoparticles (average size of 45 nm – 65 nm) by ultrasonic cavitations on mechanical properties such as ultimate tensile strength and hardness exhibited by MMNCs were analyzed. In this research, volume percentage of SiCp nanoparticles was varied at 0.4%, 0.8% and 1.2% respectively by employing ultrasonic vibrations at the amplitude of 70 μm to the melt of AA6061. The melt of AA6061-SiCp was poured into the pre heated die cavity and squeeze pressure of 105 Mpa was applied over it for a certain period while developing MMNCs. Scanning Electron Microscope (SEM) images showed the uniform distribution of SiCp nanoparticles in AA6061 matrix. Energy Dispersive Spectroscopy (EDS) in SEM confirmed the incorporation of SiCp in AA6061 matrix. The obtained results confirmed the effectiveness of ultrasonic cavitations in squeeze casting process to disperse the nanoparticles of SiCp uniformly in AA6061 matrix. The mechanical properties of MMNCs such as ultimate tensile strength and hardness exhibited an increasing trend with respect to the increase in volume percentage of SiCp nanoparticles. Thus there prevails a great scope to develop MMNCs of aluminium using ultrasonic cavitations in squeeze casting process.

Study on the Effect of Clamping Sequence on Bulk Stress Redistribution of Long Edge

For a given assembly process, fixture-related operations contribute to the dimensional variations of compliant part. When the manufactured components are within the specified tolerances, the bulk stresses distribution of the assembly are respected. In addition to fixture geometric errors and clamping forces, the clamping sequence can also affect part bulk stress redistribution. This paper presents a numerical simulation of bulk stress redistribution in a long edge assembling with different clamping sequences. A finite element model of the plate with residual stresses after quenching and stretching is constructed. The edge is milled from the numerical plate, and the edge with the initial deformation and residual stresses is ready for clamping. The contact model between the clamper and edge is constructed to simulate the practical clamping process, especially considering the friction contact between the clamper and edge. Then the edge is virtually clamped in different clamping sequences, and its deformation and bulk stresses are obtained. The simulation results show that there are differences in the stains of edge under different clamping sequences, and the edge’s bulk stresses under different clamping sequences are different with each other also. The proposed numerical model could predict the edge’s bulk stresses under different clamping sequences. It will help obtaining optimal stresses of the edge by certain clamping sequence, and help systematically improving the compliant assembling efficiency in civil aircraft industry.

Comparison Between the Numerical and Experimental Deposition Patterns for an Electrostatic Rotary Bell Sprayer

In this paper, a full 3D numerical model using ANSYS commercial software has been created to simulate the particle deposition profile for stationary and moving flat targets, assuming multiple injections of charged poly-dispersed particles. Different injection angles along three virtual rings were assumed to form a shower injection pattern. The experimental and the numerical results of deposition thickness have been presented and compared for different injection patterns. It has been found that there are some parameters, such as the total number of injection points, the radii of the rings and the fractional mass flow rate in each injection ring, which affect the numerical results of the deposition thickness and uniformity.

Negotiation in Collaborative Working Environment for the Next Generation of Product Design

Negotiation in collaborative manufacturing environments drive new ways to perform interoperability between industrial companies. The networks of SMEs are a novel segment in a highly competitive area, supported by numerous partners and applications which need to collaborate and to be interoperable. Particularly, the subcontracted small and medium enterprises (SMEs) need to be flexible towards the changes that are imposed by the major contractors, doing so at the lowest cost. This paper proposes a framework which advocates negotiations as a pillar mechanism to support innovation during the development of services in industrial collaborative working environments, and reflects the results of the European research project H2020 C2NET.

Tolerance Simulation of Thin-Walled C-Section Composite Beam in Wingbox Assembly Under Preloading

Tolerance simulation’s reliability depends on the concordance between the input probability distribution and the practical situation. Pre-loading induced changes in the probability distribution should be considered in the structure’s tolerance simulation, especially for composite structures. The paper presents a tolerance simulation method for the thin-walled C-section composite beam (TC2B) assembling under preloading, that is prescribed clamping force. Based on FEA model of TC2B, the preloading-modified probability distribution function of the R angle spring-in deviation is proposed. Thickness variations of the TC2B are obtained from the data of the downscaled composite wingbox. These parts’ variations are input to the tolerance simulation software, and the final assembly variations are obtained. The assembly of the downscaled wingbox illustrates the effect of preloading on the probability distribution of the R angle spring-in deviation. The results have shown that tolerance simulation with the modified probability distribution is more accurate than the initial normal distribution. The tolerance simulation work presented in the paper will enhance the understanding of the composite parts assembling with spring-in deviations, and help systematically improving the precision control efficiency in civil aircraft industry.

CFD Multiphase Flow Modelling of Air Porosity Defect Formation During High-Pressure Die-Casting Filling Process

High-Pressure Die-Casting (HPDC) is an important process for manufacturing high-volume and low-cost components. In this process molten metal is injected at high speed under high pressure into the die cavity, which often leads to entrapment of air into the liquid metal. This will cause air porosity after solidification, the main defect in the parts made by HPDC. The aim of this work was to develop a CFD multiphase flow simulation method to numerically study the air porosity defect formation in HPDC. Some numerical models have been developed to predict the air porosity defect in HPDC. However, most of them are limited to one phase flow model which could only simulate the filling process of liquid metal. In this study both the bulk fluid and surrounding air were modeled by a 3D multiphase flow model. The proposed model can describe the entrapment, advection and coalescence of air bubbles within the melt, and thus has the ability to accurately simulate the air porosity defect formation in HPDC. In the present paper, an incompressible-compressible two-phase flow model was developed. The numerical benchmark test of a broken dam problem was used to demonstrate the effectiveness of the proposed model. Then numerical model was applied to simulate a high speed water filling process. Results of the modeling were compared with corresponding experimental data and good agreement has been found.

MATLAB Image Processing as a Viable Tool to Study Low Surface Roughness

The purpose of this paper is to present the results of a study comparing an old technique for measuring low surface roughness with a new technique of data acquisition and processing that is potentially cheaper, quicker and more automated. It offers the promise of in-process quality monitoring of surface finish. Since the late 1800s, researchers have investigated the light scattering effects of surface asperities and have developed many interferometry techniques to quantify this phenomenon. Through the use of interferometry, the surface roughness of objects can be very accurately measured and compared. Unlike contact measurement such as profilometers, interferometry is nonintrusive and can take surface measurements at very wide ranges of scale. The drawbacks to this method are the high costs and complexity of data acquisition and analysis equipment. This study attempts to eliminate these drawbacks by developing a single built-in MATLAB function, to simplify data analysis, and a very economically priced digital microscope (less than $200), for data acquisition. This is done by comparing the results of various polishing compounds on the basis of the polished surface results obtained from MATLAB’s IMHIST function to the results of stylus profilometry methods. The study with the MATLAB method is also to be compared to 3D microscopy with a Keyence microscope. With surface roughness being a key component in many manufacturing and tribology applications, the apparent need for accurate, reliable and economical measuring systems is prevalent. However, interferometry is not a cheap or simple process. “Over the last few years, advances in image processing techniques have provided a basis for developing image-based surface roughness measuring techniques” [1]. One popular image processing technique is through the use of MATLAB’s Image Processing Toolbox. This includes an array of functions that can be used to quantify and compare textures of a surface. Some of these include standard deviation, entropy, and histograms of images for further analysis. “These statistics can characterize the texture of an image because they provide information about the local variability of the intensity values of pixels in an image. For example, in areas with smooth texture, the range of values in the neighborhood around a pixel will be a small value; in areas of rough texture, the range will be larger. Similarly, calculating the standard deviation of pixels in a neighborhood can indicate the degree of variability of pixel values in that region” [2]. By combining the practices of interferometry with the processing techniques of MATLAB, this fairly new method of roughness measurement proved itself as a very viable and inexpensive technique. This technique should prove to be a very viable means of interferometry at an affordable cost.