2. Structure of the course paper

According to the Appendix 5 the designed course paper should contain:

1. Title page.

2. Contents.

3. Abstract.

4. Introduction.

5. Main part.

1. Choice of material and type of specimens for pendulum-type impact testing machine (Appendix 1).

2. Construction of serial curves on the base of defined data of impact toughness for different materials (Appendix 2).

3. Determination of cold brittleness temperature for different materials on the base of dynamic bending tests.

4. Determination of influence of notch type of impact specimens on fracture character.

5. Macrofractographic analysis of specimens fractures for dynamic tests (Appendix 3).

6. Comparison of fractures of different steels at the same tests temperatures.

7. Determination of impact specimens test temperature influence on fracture character.

8. Microfractographic analysis of specimens fractures for dynamic tests (Appendix 4).

9. Determination of impact specimens test temperature influence on fracture character.

- Conclusions.

- Resources.

- Appendixes.

3. Contents of the course paper parts

3.1. Introduction

In the introduction to the course paper it is necessary to sketch the role of problem of brittle fracture in result of difficult conditions of work of machines and buildings at the constant increase of working stresses, rise of dynamic loadings and decrease of working temperatures. It is necessary to formulate the task of the work. The introduction should be about 2 pages.

3.2. Main part

3.2.1. Choice of material and specimens type for pendulum-type impact machine testing, determination of impact toughness

The bar reinforcement for reinforced concrete constructions is made from the hot-rolled and heat-strengthened metal of a certain strength level and proper steel grades. In the given the course paper materials for investigation are reinforcement bars of А400 class (steel 25Г2С in hot-rolled state), А600 class (steel 80С, 20ХГ2Т in hot-rolled state) and Ат600С class (25Г2С in heat-strengthened state after rolled heating and furnace heating) of 18mm diameter.

The investigated material should be chosen in accordance with the student’s credit book in Appendix 2/

In practice, steel toughness is characterized by the impact bending tests results. The impact toughness is a work spent on deformation of notched specimen impact bending failure of notched specimen in result of its testing on pendulum-type impact machine.

Shape and sizes of impact specimens (fig. 3.1), requirements to the test machines, order of testing at normal, low and high temperatures and analysis of obtained results are regulated by GOST–9454–78.

Fig. 3.1. Specimens for the impact bending test.

a – U-notched specimen, «Menazhe» Type I;

b – V-notched specimen, Type IV;

c – T-notched specimen, fatigue crack.

Impact toughness can be found by the formula:

,

where is the work spent on specimen failure at the test, kgm,

F is the cross-section area in the notched place before the test, сm².

The values of impact toughness are defined to within 0,1 kgmсm² (at the International system of units 1 kgmсm² is equal to  10^-1 МNm/m²).

The specimen of type Ι is used as the basic one, so called «Menazhe» specimen. The GOST specifies the obligatory conducting of parallel tests on the specimen of type Ι at determination of impact toughness on the specimens of type II, III, IV.