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This document deals with the development of drilling tools by means of CAD and CAE technologies. At first, a brief overview of various design procedures of 3D drill models is presented, possibilities of measurement of force and moment loading during drilling are mentioned, a chip formation mechanism is briefly described and then a list of commonly used explicit (mesh) finite element methods used for cutting simulations is presented. A meshless SPH method have been selected for this work. Although it is able to handle the large deformations easily, it has been used for cutting simulations very rarely and only an orthogonal cutting simulations related information can be found in scientific databases. It has been demonstrated on the orthogonal cutting simulation of A2024-T351 alloy that was also the starting point for SPH simulation of drilling. The following is a decription of the design, simulation and prototyping of new drilling tools - drills with three and two cutting edges and an internal chip channel. This document is focused in detail on the variant with two cutting edges for which SPH drilling simulation has also been performed. Some drawbacks related to more precise chip simulation demands have been revealed, especially a rapid increase in number of SPH elements followed with prolongation of a computational time. Information related to the design of the drilling head with two cutting edges were then used to create the patent application.

The purpose of the present study is to develop and explain a teaching aid for Spanish word recognition, to be presented as advance preparation for large-exposure reading.

Data for this study was gathered by questionnaires completed by thirteen drill team directors, thirty-eight women physical education department heads at schools not having a drill team, fifty-six girls who were members of the precision drill team at their school and 416 girls who were not members of a precision drill team. Drill team directors indicated strong feelings of success as to the organization and administration of their groups and also were positive as to the merits of precision drill teams in the junior high schools. The majority of the physical education department heads did not desire that a precision drill team be organized at their school although many indicated that they realized some of the merits of such groups. Administrative philosophy appeared to be the biggest reason why these schools did not include a drill team in the school curriculum. Drill team members believed strongly in the benefits of a junior high school drill team, indicating their feelings of success and personal satisfaction as a result of their participation. The majority of non-drill team members indicated that they would like to be a drill team member and showed strong support for the drill team at their school. Findings indicated that all of the respondents were in harmony as to the merits of a drill team and nearly any school desiring a drill team would be able to with the only possible restriction being lack of facilities.

<p>The aim with this study was to investigate the effects a change of manufacturing process would have on the mechanical properties of drill bits made of a WC/Co composite used for stone cutting. The method used today is sintering, where the material is heated in a conventional sintering oven. The other method was microwave sintering, where the material is heated by radiation in the microwave region. Also an investigation of the manufacturing cost were made.</p><p>The main difference between the two heating methods is that the conventional way is a rather slow process and the microwave method is very fast. The material is also heated homogeniously in the method with mirowaves, aposed to the case with the conventional sintering where the material is heated from the outside in.</p><p>This makes the material harder and more wear resistent. Another positive effect is that the pysical properties of the drill bits is easier to controll, because of the very small grain growth due to the short process time.The cost of manufacturing these drill bits by microwave sintering does not exceed the cost of the conventionall sintering.</p>

Graduation date: 1991

This Master Thesis has been performed at Atlas Copco Rock Drills AB, Örebro and at Linköping University, Sweden from February 2010 through August 2010.The project deals with performance improvement of hydraulic rock drill machine manufactured by Atlas Copco Rock Drills. Atlas Copco Rock Drills AB is a world leading supplier of percussive rock drilling equipment for surface and underground applications. HOPSAN, a software developed at Linkoping University, provides an integrated simulation environment for simulation of fluid power systems. During the work, a HOPSAN model of a piston accumulator has been developed and its performance with a rock drill has been studied. Furthermore, the fatigue strength calculations of a piston accumulator has been made on the basis of stress analysis performed using the ANSYS software. One of the rock drills of valveless type, developed at Atlas Copco Rocktec Division works at higher efficiency than the conventionally used rock drills. But the problem with this type of drill is that the piston swings between two large and highly pressurized oil volume which causes strength problems in the housing of the rock drill. The aim of this work is to achieve the higher efficiency of the rock drill without having any strength problems. Therefore, some study and research is proposed to replace the large oil volume by one or two piston accumulators. This thesis work involves modelling, simulation, design and fatigue strength calculations of a piston accumulator and its implementation to the rock drill. Optimization of the piston accumulator has also been conducted while working with the rock drill so that highest possible eciency could be achieved. The performance of the rockdrill with piston accumulator has been analyzed and results are studied. In the end, a short fatigue life calculations are performed and results are discussed. Prior to fatigue life calculations, a transient dynamic stress analysis has been performed and stress amplitudes are identified which contributes to the accumulated damage to piston in accumulator.

The aim of this thesis work was to design and evaluate a wear test method for cemented carbides inserts used in rotary drilling. An appropriate in-house wear test method would provide a better understanding of the wear mechanisms limiting tool life in real drilling. The test method should be easy to use and be able to distinguish between wear of insert materials with different microstructure and properties. The literature study showed few published articles about wear tests and mechanisms concerning rotary drill bit inserts. These methods included two standard wear tests; ASTM G65 and ASTM B611. Furthermore, a modified ASTM G65 test was found as well as an impact-abrasion test. In this work the modified ASTM G65 test, using a rock counter surface, was evaluated in order to understand if the method would mimic the wear of cemented carbides used in rotary drilling. The test method was further developed and showed high repeatability. Measured weight losses showed that the test could distinguish between two common rotary grade materials with a small difference in hardness but with different microstructures. The wear of the tested materials was analyzed with scanning electron microscopy and compared with rotary drill bit inserts collected from the field. The modified test method proved able to produce wear by mechanisms very similar to those found on field worn inserts. Identified wear mechanisms included cracking, fragmentation and spalling of WC grains as well as embedded fragments of WC grains on the surface. In addition, the binder phase was removed and adhered material from the counter surface was detected.

The aim with this study was to investigate the effects a change of manufacturing process would have on the mechanical properties of drill bits made of a WC/Co composite used for stone cutting. The method used today is sintering, where the material is heated in a conventional sintering oven. The other method was microwave sintering, where the material is heated by radiation in the microwave region. Also an investigation of the manufacturing cost were made. The main difference between the two heating methods is that the conventional way is a rather slow process and the microwave method is very fast. The material is also heated homogeniously in the method with mirowaves, aposed to the case with the conventional sintering where the material is heated from the outside in. This makes the material harder and more wear resistent. Another positive effect is that the pysical properties of the drill bits is easier to controll, because of the very small grain growth due to the short process time.The cost of manufacturing these drill bits by microwave sintering does not exceed the cost of the conventionall sintering.

This thesis work sought to find a tribological testing method suitable for cementedcarbide drill bit inserts used when drilling rock. A review of the literature publishedon the matter showed that there are quite a few test methods developed for wearstudies with cemented carbides, but most of them were not designed for the rockdrilling industry. Published studies performed with the found methods and articleswith analyzed field tests have been studied. It is generally agreed upon that the stepsof wear is that the binder disappears first, followed by removal of carbide grains. Themechanisms of binder phase and carbide grain removal is somewhat debated, butalmost every study observes fracture of the carbide grains. The wear test created inthis thesis was shown to give wear linear with time, but not with load. The newmethod was shown to be capable of distinguishing between different cementedcarbides worn in three body abrasion against different rocks. Analysis of the wornsamples shows that there are similarities with bit inserts worn in field testing. Many ofthe observations made during the analysis are also similar to observations inliterature.