The continuous development of hot forming tool steels has resulted in steels with improved mechanical properties. A change in alloying composition, primarily a decreased silicon content, makes them tougher and more wear resistant at elevated temperatures. However, it is at the expense of their machinability. The aim of this study is to explain the mechanisms behind this negative side effect. Hot work tool steels of H13 type with different Si content were characterised mechanically, and evaluated analytically and by dedicated machining tests. Machining tests verified that materials with low Si content displayed reduced machinability due to their stronger tendency to adhere to the cutting edge. Three hypotheses were tested. The first hypothesis, that the improved toughness of the low Si steels is the reason behind their relatively poor machinability, was rejected after machining tests with one low Si steel heat treated to the same relatively low toughness as conventional hot work tool steels. The second hypothesis, that a change in oxidation properties, also associated with the change in Si composition, lies behind the reduced machinability was investigated by dedicated tests and evaluations. It was found that the oxide thickness increased with reduced Si content and that there was an enrichment of Cr at the oxide/steel interface. The differences in oxide thickness and the possible differences in oxidation properties may influence the machinability of the materials through their different abilities to adhere to the cutting edge. The third hypothesis, that a high enough temperature to initiate phase transformation from ferrite to austenite is generated during machining of the tool steels, was also investigated. This may lead to a reduced machinability because higher austenite content is directly related to higher compressive stresses and higher cutting forces. This causes accelerated tool wear. This hypothesis was verified by ThermoCalc calculation of austenite content in the steels, which showed a good agreement with Gleeble compression tests and cutting force measurements. This thesis confirms that a reduced Si content in conventional H13 steel improves the toughness, reduces the oxidation resistance and lowers the ferrite-to-austenite transformation temperature. The reduction in austenite temperature is probably the most important factor behind the reduced machinability.

Chromium martensitic hot-work tool steel (AISI H13) is commonly used as die material in hot forming techniques such as die casting, hot rolling, extrusion and hot forging. They are developed to endure the severe conditions by high mechanical properties attained by a complex microstructure. Even though the hot-work tool steel has been improved over the years by alloying and heat treatment, damages still occur. Thermal fatigue is believed to be one of the most common failure mechanisms in hot forming tools. In this thesis tools used in hot forging and die casting were examined to determine damage, material response, thermal fatigue crack initiation and propagation. Different chromium martensitic hot-work tool steels, heat treated at four different austenitizing temperatures were experimentally tested in thermal fatigue and isothermal fatigue. The materials were then evaluated using X-ray line broadening analysis and transmission electron microscopy to explore the relation between fatigue softening and the change in microstructure. The high temperature fatigue softening was also simulated using an elasto-plastic, non-linear kinematic and isotropic model. The model was implemented in a numerical simulation to support the integration of die design, tool steel properties and its use. It was found that the dominant damage mechanisms in the investigated tools were thermal fatigue and that tool material experiences a three stage softening at high temperature loading. The primary stage was concluded to be influenced by the dislocation density and the second stage by the temper resistance i.e. carbide morphology. The microstructural changes during the softening stages were also connected to the non-linear kinematic and isotropic model. The general aim of this thesis is to increase the knowledge of the chromium martensitic hot-work tool steel damage, performance and microstructure.

The primary intent of this study was to gain insight into the developmental nature of spatial perception and representation. More specifically, the work presented here examined 1) the age-related ability to modulate peri- and extrapersonal space via hand and tool use, 2) the adjustment period associated with extending and retracting spaces, and 3) the effect of tool length on modulation of space. Seventy children representing age groups 7-, 9-, 11 years and adults were presented with two experiments using an estimation of reach paradigm involving hand and tool conditions and a switch-block of the opposite condition. Experiment 1 tested Hand and Tool (20cm length) estimation and found a significant effect for Age, Space, and an Age x Space interaction (ps <.05). Both children and adults were less accurate in extrapersonal space, indicating an overestimation bias. Interestingly, the adjustment period during the switch-block condition was immediate and similar across age. Experiment 2 was similar to Experiment 1 with the exception of using a 40cm length tool. Results of 55 participants also revealed a difference in estimation responses between Age groups (p <.05); 7- and 9-year-olds were similar and less accurate than adults, and 11-year-olds were not different from any other age group. There was also a difference in Space (p <.05), revealing that participants underestimated their reaching abilities with higher accuracy in extrapersonal space. Interestingly, whereas participants overall overestimated with the 20cm tool, they tended to underestimate while using the 40cm tool. This finding suggests that participants were less confident when presented with a longer tool, even though the adjustment period with both tool lengths was similar. Considered together, these results hint that: (1) children as young as 6 years of age are capable of re-scaling peripersonal space via tool use in the context of estimation reach, (2) the adjustment period associated with extending and retracting spaces is immediate rather than gradual, and (3) tool length may influence confidence of participants, shifting the general direction of error from overestimation with a 20cm tool to underestimation with a 40cm tool.

No description available.

Background: Renacimiento, Mexico in the state of Nuevo Leon is home to approximately 1,000 families who currently experience a host of social, health, and community challenges that span both rural and urban Mexico. The state has committed to initiate the construction of a community health clinic. Methodology: In preparing for the clinic, a needs assessment instrument and associated materials were developed for community members and volunteers to administer to residents within Nuevo Leon. Results: A culturally sensitive survey instrument and associated documents were created with consideration for low-literacy participants and with a wide variety of topics in the areas of individual, women’s, children’s and community health. Conclusions: The creation of this needs assessment survey provide insight to stakeholders in Mexico and abroad who stand to benefit from learning what community residents’ perceive as their greatest needs. The results from the survey will provide the first ever documentation of this unique community’s health status and will demonstrate areas of need within which the community health clinic can focus their efforts.

A component is built to be reused and reusability has significant impact on component generality and flexibility requirement. A component model plays a critical role in reusability of software component and defines a set of standards for component implementation, evolution, composition, deployment and standardization of the run-time environment for execution of component. In component based development (CBD), standardization of the runtime environment includes specification of component’s interfaces – general and domain specific run-time services. For rapid development of component based system for distributed information systems, COM+ and .NET technologies introduced the idea of Software Component Services that are achieved by proxy objects which intercept message calls between components to provide service like transaction handling, security management, etc. An embedded real-time system (ERTS) designed for a specific purpose in which software tasks have hard real-time constraints to execute and it interact directly with its environment via buses, sensors and other devices. In an embedded real time system, it is great importance to ensure that all tasks of the software system should respond within the time limits. Component based development process have vital role in development of embedded real time system and recently software component models applied in the embedded real-time systems (ERTS) and introduced software component services (SCS) for ERTS. The purpose of this Master thesis is to investigate how to make tool that targets smart device projects in Microsoft Visual Studio and generates proxy objects that can be compiled with Microsoft Visual Studio.NET. The tool generates a complete set of files for a Microsoft Visual Studio smart device project within solution, including both source code and configuration files according to a specific version of Visual Studio by invoking Visual Studio’s automation object model. The tool also generates code for simple logging services for the .NET component running on top of the .NET Compact framework.

No description available.

The main goal of this thesis is to propose a strategy which can integrate the precision hydrodynamic polishing system with an ordinary CNC machine tool. This integrated CNC machine tool is capable of applying the hydrodynamic polishing process, which is a high-precision machining method, to compensate the form error on a work surface to improve its form precision. With such a compensation capability, a low-cost CNC machine tool may play the function of precision machining as well as an expensive CNC machine tool does. It is hoped that with this function equipped in a CNC machine tool the international competition of the domestic machining industry can be enhanced. The complete integrating scheme is composed of three parts. The first part is the hardware of polishing system, which is required to attach to the CNC machine tool. The second one is the software developed in this thesis. It includes the codes to generate the commands to control the CNC machine tool and the attached polishing system. The final one is coordinating system that is to synchronize the actions of the CNC machine tool and polishing system. It is done by requiring the polishing system to match the actions of machine tool through measuring the configuration of machine tool consistently. Because of the first and third parts, no modification to the machine tool is needed and the requirement to read the internal information of CNC controller is waved. This will significantly reduce the complexity in implementing the integrating job. When properly integrated with the required sensors, the software developed in this thesis can harmonize the actions of the polishing system and machine tool to execute the form error compensation task. The software will automatically generate the commands for the polishing system and machine tool based on the geometric and material data of work. It does not require the user to fully comprehend the function of the CAM software and the details of polishing process. This will obviously reduce the skill requirement of operator and facilitate the use of the integrated system. Since the CNC machine tool only plays the function of offering the three translational motions (in X, Y, and Z directions), the application of this strategy to an ordinary CNC machine tool is straightforward.

Vibration assisted cutting (VAC) is a new metal machining technique in recent years, where high-frequency and low-amplitude vibrations are imposed to the cutting tool or the workpiece. It has many advantages than conventional cutting (CC), especially improvements in surface finish and tool life. Nowadays, the use of VAC is a good strategy for micro-machining due to long tool life and high product dimension accuracy. This study presents an experimental investigation of the VAC in micro milling. The tool wear, surface roughness, and burr formation are investigated for different cutting parameters under conventional and vibration assisted cutting. When the vibration speed is higher than 3 times of the cutting speed, the tool life can be prolonged in this study. The experimental results show that VAC process has better surface finish (43.51% reduction in value) compared to that in CC, when the cutting conditions are feed of 4 £gm/rev and cutting speed of 3.39 m/min. It is also found that VAC can diminish the formation of burr formation. By introducing MQL to VAC, the tool life is extended because the MQL could reduce the friction between the tool and workpiece.

A strategy was proposed to suppress the wear effect of tool in a polishing process. So, machining rate of work pieces in polishing process would keep constant. With this strategy applied to HDP, stable machining rate will bring more advantaged for precision engineering. This study mainly discussed by two parts. First, the planning of the rock-and-roll motion and a wear analysis for tools is talked about. Second is discussing about experiment further. In first part, in order to increase tool¡¦s lifetime, expanding tool wear region by rock-and-roll motion is adopted. Meanwhile, simulate the wear behavior to develop a method of removing tool¡¦s materials in expectant form. In second part, there are two targets to compare with first part, one is the effect of planning of tool¡¦s materials removing and the other is the improvement of suppressive wear effect for polishing tool and stabilizing removal rate of work pieces in rock-and-roll motion. The result of experiments shown that planning of tool¡¦s materials removing is working, the radius of curvature and roughness of tool is nearly stable, and there are some effects in removal rate on work pieces. The result of experiment of rock-and-roll motion verified that the wear theorem for tools and prove improvement of wear is working. So, the goal of suppression of wear effect for polishing tool by expanding tool wear region by rock-and-roll motion is feasible.