Fatih GÜNDÜZ 030060144 (10th week)

Dial Indicators:

Dial Indicatorsmagnify small movements of a plunger or lever and show this magnified movement by means of a pointer on a graduated dial. This direct reading from the pointer and graduated dial gives the operator a quick, complete and accurate picture of condition of item under test. Dial Indicators are used to check the dimensional accuracy, of workpieces in conjuction with other equipment such as gauge blocks, to check straightness and alignments of machines and equipment, to set workpieces in machines to ensure paralelism and concernity and for a host of other uses too numerous to list completely.

(Workshop Processes, Practices and Materials, B. J. Black, p.108)

Grain Boundary Sliding:

At high temperatures and low strain rates, sliding occurs along the grain boundaries of polycrystalline materials. In creep tests on pure metals at low stresses, as much as 30 percent of the total strain may be due to grain boundary sliding. At temperatures close to the melting point where there is a high equilibrium concentration of lattice vacancies, and self diffusion is rapid, polycristalline materials may deform by diffusional creep. In this deformation mode atoms diffuse to boundaries normal to the force and vacancies migrate to boundries parallel to the force axis. The result is crystal elongation in the direction of the applied force due to diffusional creep.

(Failure of materials in mechanical design, J.A. Collins, p.33)

Grain Boundary Strengthening:

Grain boundaries are barriers for the movement of dislocations. As the crystal orientation in the neighbouring grain is diffrent, a dislocation cannot simply enter it. The stress field of the dislocation may initiate dislocation movement in the neighbouring grain, but if the slip systems are less favourabl oriented there, a larger stress is needed to move dislocations than in the first grain.

If a slip system is activated in a crystal, several dislocations are moving on one slip plane in the same direction and can pile up at a grain boundary. Thus it is plausible, as will be explained below, that the strength of metals increase with decreasing grain size. This strengthening mechanism is called grain bounsary strengthening or strengthening by reduction of the grain size.

(Mechanical behaviour of engineering metarials, J. Rösler, H. Harders, p.200)

Breakout Board:

As the name implies, this type of prınted circuit board performs a brteakout of the signals present on each of the pins on the db-25 connection coming from the computer's parallel ports. These boards are also commonly referred to as a BOB, Which is short for breakout board. One of the primary functions of any breakout board is to provide some form of electrical isolation between the computer and the controller. This is critical as any anomalies in wiring or spikes in voltage will isolate the damaging electricity from migrating back to the physical port on the computer. These types of boards also provide convinient connections for the user to interface with the components. Some breakout boards have more features than others, Bu all provide basic connectivity required for step and direction signaling for each axis and phased output signaling for each motor - all via a db-25 input port. Note that the definition of port is generally used for the primary and secondary parallel port esed on the controller's computer; pins are the individual wires on the port. In some instance, the use of an additional port is used to provide more inout/output functionality, as is the case in the use of a plasma torch height controller for independent Z axis or if encoders are used in conjuction with stepper motors, etc. When more than one port is used, There are denoted ports 1 and 2.

(CNC Machining Handbook: Building, Programming, And Implementation, A. Overby, p.72)