Machine Elements

Instructor:     Dr. Sotiria ChouliaraTime & Classroom:  M ‐W‐ ‐, 09:00‐11:00, Classroom: B2 E‐Mail: schoul@uth.grWeb Site: http://www.mie.uth.gr/n_ekp_yliko.asp?id=37

OBJECTIVES:Machines consist of interrelated elements. This course will focus on design of important conventional machinedesign elements. The basic principles from the fields of Statics, Dynamics and Mechanics of Materials areemployed in the design of standard mechanical components subjected to operating force and moment fields.This course will highlight the adaptation of theoretical relationships/formulas to practical design problems.

EVALUATION SCHEME:The course grade will be based on one term test (30%) and the final exam (70%), both ‘’close‐book’’ exam type.

Course Outline

‐Στοιχεία Μηχανών, Παπαδόπουλος Χρήστος, Εκδόσεις Τζιόλα‐Shigley's Mechanical Engineering Design (McGraw‐Hill Series in Mechanical Engineering)‐Fundamentals of Machine Component Design, R.C. Juvinall and K.M. Marshek

EVALUATION SCHEME:

11/2/2019 week 01 Fundamental Topics from Mechanics of Materials18/2/2019 week 02 Static Failure Theories25/2/2019 week 03 Fatigue Failure Theories4/3/2019 week 0411/3/2019 week 0518/3/2019 week 0625/3/2019 week 071/4/2019 week 088/4/2019 week 0915/4/2019 week 106/5/2019 week 1113/5/2019 week 1220/5/2019 week 1327/5/2019 week 14 Review

course plan

Screws and Fasteners

Shafts

Belts (flexible mechanical elements)

Spur Gears

Engineering Design

‐Dimensions:

y

n

Potential Critical Points/Cross‐Sections:

‐maximum load (force or moment)

‐geometric discontinuities

‐stress concentration factors

n συντελεστής ασφαλείας(safety factor)

Mechanics of materials ~ Machine elements components 

Link AB is to be made of a steel for which the ultimatenormal stress is 450 MPa. Determine the cross‐sectional area of AB for which the factor of safety will be 3.50.Assume that the link will be adequately reinforced around the pins at A and B.

1. The shaft has constant speed, FB=?

2. Reactions forces at O, C

3. Bending moments diagrams

4. At the maximum bending momentpoint determine maximum bendingstress and maximum torsional stress

5. Find σe

**Μηχανική Υλικών, Ν. Αράβας,Παρ. 6.3 Διαστασιολόγηση Ατράκτων

1. The shaft has constant speed,tensions in the belt in pulley B

2. Reactions forces at O, C

3. Shear force and Bending momentsdiagrams

4. At the maximum bending momentpoint determine maximum bendingstress and maximum torsional stress

5. Find σe

**Μηχανική Υλικών, Ν. Αράβας,Παρ. 6.3 Διαστασιολόγηση Ατράκτων

V‐ belts system

Three steel bolts are to be used to attach the steel plate shown to a woodenbeam. Knowing that the plate will support a 110‐kN load, that the ultimateshearing stress for the steel used is 360 MPa, and that a factor of safety of3.35 is desired, determine the required diameter of the bolts.

A torque of magnitude T=900 N.m is appliedat D as shown. Knowing that the allowableshearing stress is 50MPa, determine therequired diameter of shaft AB and shaft CD.

Shaft BC is hollow with inner and outer diameters of 90 mm and 120mm, respectively. Shafts AB and CD are solid and of diameter d. Forthe loading shown, determine (a) the maximum and minimumshearing stress in shaft BC, (b) the required diameter d of shafts ABand CD if the allowable shearing stress in these shafts is 65 MPa.