Deniz Alsan 030080093 1.st week

1- Viscoelastic behaviour - Group : Material

previous answer:


For a component subjected to a uniaxial force, the enginnering stress in the material is the applied force divided by the original cross-sectional area. The engineering strain changes with depending on the elasticity. Polymeric material in axhibit mechanical properties which come some where between these two ideal cases and hence they termed viscoelastic . In a viscoelastic material th stress is a fuction of strain and time.     (Plastic Engineering , R. J. Crawford ,Second editon , pg 42)

Better answer:

Viscoelastic behaviour is a combination of elastic and viscous behaviour where the applied stress results in an instantaneous elastic strain followed by a viscous, time-dependent strain.

(Dielectric elastomers as electromechanical transducers, Federico Carpi, Danilo De Rossi, Roy Kornbluh  p261)


2- Finite Elements Analysis - Group : Analysis method
previous answer:


FEA is a numerical method which provides solutions to problems that would otherwise be difficult to obtain.
In terms of fracture, FEA most often involves the determination of stress intensity factors. FEA uses complex
system of points called nodes which make a grid called a mesh. This mesh is programmed to contain the material and structural properties which define how the structure will react to certain loading conditions.


(World Congress on Medical Physics and Biomedical Engineering 2006, 6. cilt p887)


Better answer:

FEA is a technique used by engineers to estimate the responses of structures and materials to environmental
 factors such as fluid flow, forces, heat and vibration. It is possible to model complex mechanical components
 by subdividing a component into small "finite" elements and analyzing the component as an assembly of these small, simple elements.
(How Reliable Is Your Product?: 50 Ways to Improve Product Reliability, Mike Silverman, p155)

3-Gantry Robot - Group: Manufacturing
previous answer (better)

A gantry robot operates over a clearly defined rectangular area. It picks up objects from any point in the area and sets them down at another point in the area. The tool (often a gripper) is suspended from a small trolley-like frame, and can be lowered and raised. The frame has wheels and runs on a pair of rails so that it can travel from one side to the opposite side. This set of rails is on a larger frame at right angles to the first set, so the smaller can be moved to any point within the area. Thus the location of the tool is defined by two coordinates, its x-position and y-position. Gantry robots are used in industry when very heavy loads are to be handled.
(Bishop O., Robot Builder’s Cookbook, page 16)

new answer:

Pick and place robots  are typically stationary, pedestal-mounted robots. Therefore their work envelope is limited. To increase the work envelope and serve more machines, a (pick-and-place) robot can be installed on a gantry crane.

(Shimon Y. Nof, Handbook of industrial robotics, p960)


4 - Epoxy - Group : Material
no previous answers available on system

Epoxy is a two-part material consisting of a resin and a hardener. When mixed together, they polymerize to form a hard plastic material. Modified with the proper additives and paired with appropriate fiberglass materials, epoxy/hardener mixture has a consistency prior to setting anywhere from firm, thick and clay-life to thin and syrupy. Many epoxies on the market today have a mix ratio of 5 parts resin to 1 part hardener. Although 4:1, 3:1, 2:1, and 1:1 epoxies are also available.

(Esterle P., Maintain and Improve Your Powerboat: 100 Ways to Make Your Boat Better, p17)


5 - Wankel Engine - Group : Manufacturing
previous answer

The Wankel Engine is a rotary combustion engine, developed from the work of Felix Wankel. The triangular rotor has a centrally placed internalgear that meshes with as un gear that is part of the engine casing. An eccentric that is an integral part of the output shaft constrains the rotor to follow a planetary motion about the output shaft. the gear ratios are such that the output shaft rotates at three times the speed of the rotor and the tips of the rotor trace out the two-lobe epitrochoidal shape of the casing. the compression ratio is dictated geometrically by the eccentricity of the rotor and the shape of its curved surfaces. The convex surfaces miximise and minimise the sealed volumes, to give the highest compression ratio and optimum gas exchange. A recess in the combustion chamber provides a better-shaped combustion chamber.

The advantages of the Wankel engine are its compactness, the apparent simplicit, the ease of balance and the potential for high outputs by running at high speeds. The major disadvantages of the Wankel engine are its low efficiency (caused by limited compression ratios) and the high exhaust emissions resulting from the poor combustion chamber shape.

(Stone R., Introduction to Internal Combusiton Engines, 2nd Ed., pg.17-18,)

better answer:

Wankel engine is a rotary combustion engine originated by a German engineer, Felix Wankel, in 1924. It is used where compactness and higher engine speeds are required, such as in racing cars. The engine is well balanced and runs smooth. However, problems related to higher heat transfer, sealing and leakage exist. The major components of the Wankel rotary combustion engine are shown in Figure 18.3(a). It consists of three rotating arts: the triangular-shaped rotor having the internal ring gear, the output shatf with eccentric and the flywheel. The stationary parts are two lobe centre housing, called the stator, with the intake and exhaust ports, two side housings with the fixed timing gear on one side of the housing, called the sun gear. The rotor revolves directly on the eccentric within its stator in such a manner that its apexes always make contact with the surface of the stator. The internal timing gear of the rotor and eccentric shaft rotations. The rotor with its planetary motion about the sun gear drives the output shaft three times faster.
(H.N. Gupta, Fundamentals of Internal Combustion Engines pp565, 566)