Compression Test of Timber.

WORLD UNIVERSITY OF BANGLADESH

Assignment

    Prepared By:                                                  Submitted To                                                                                                                                                                                                                 
Name: MOHAMMED ABDUR RAZZAK                                 Name:  JAHANGIR  ALAM

Roll No:  3326                       Designation:            Lecturer

Registration No: WUB/10/13/60/3326   

Batch No: 60/C        Semester No: Four

Year: second                        Date of Submit ion: 

Introduction :

In tension and compression test, attempt is made to apply an axial load to a test specimen so that uniform tress distribution can be ensured over the critical section. In such tests the specimen is subjected to a gradually increasing ( i.e static ) uniaxial load until failure occurs. The static tension and compression tests are the most commonly made and are among the simplest of all the mechanical tests. These tests provide almost all the fundamental mechanical properties for use in design. The use of the tension as against the compression test in all probability is largely determined by the type of service to which a material is to be subjected. Metals, for example, generally exhibit relatively high tenacity and are therefore better suited to and are more efficient are resisting tensile loads than material of relatively low tensile strength. For brittle materials such as mortar, concrete, brick and ceramic products, whose tensile strengths are low compared with their compressive strengths, and which are principally employed to resist compressive forces, the compression test is more significant and finds greater use.

Stress :

Stress ( Ó ) is defined as the intensity of the internal distributed forces or components of forces that resist a change in the form of a body. Stress is measured in terms of force per unit area (P/A), e. g. psi, kg/cm², N/mm² etc.

Strain :

Strain is defined as the change per unit of length in a linear dimension of a body. It is a ratio, or dimensionless number, and is therefore the same weather measured in inches per inch of length or length or centimeters per centimeter, etc. (Strictly, this definition of strain is limited and is applicable to axial strain only. However, this definition is provided for easy conceptualization by the students; a more general definition is that strain is the intensity of the definition- whatever be the nature of deformation.)

01.       OBJECTIVES:

i.                   To test a Timber specimen under compressing loading parallel to the grain.

ii.                 To draw strain-strain diagram.

iii.              To study the failure characteristics of the timber specimen.

iv.               To determine the following properties of the timber specimen.

02.       APPARATUS:

i.                  Compresometer   ii.  Steel scale iii.  Slide calipers

03.       MACHINE:

i.                  The universal Testing machine.

04.       SPECIMEN:

47mmx47mmx153mm Wooden Block (ASTM D 143)

05.       PROCIDURE:

i.                  Measure the size of  the specimen by a slide calipers

ii.               Record gage length and multiplication factor of the Compresometer.

iii.            Attach Compresometer with the specimen and set the specimen in proper position of the testing machine.

iv.             Adjust the Compresometer dial to read zero.

v.                Apply load continuously at a uniform speed until failure and read the Compresometer 10 KN intervals.

vi.             Take off the Compresometer when breaking starts.

vii.          Record the maximum load and the final length between the gauge marks.

viii.       Note the characteristics of the fractured surfaces and draw the extended surfaces of the failed specimen and show the failure pla

Data sheet for Compression test for timber:

Gauge Length: 153 mm

Cross-sectional area of the specimen: 2209 mm

Observation No	Load in KN	Compresometer	Load	Deformation in mm	Stress KN/mm²	Strain	Remarks
01	0	0	0	0	0	0	0
02	10	2	10	.02	4.53x10ֿ ֿ³	0.13x10ֿ ֿ³
03	20	5	20	.05	9.05x10ֿ ֿ³	0.33x10ֿ ֿ³
04	30	8	30	.08	13.58x10ֿ ֿ³	0.52x10ֿ ֿ³
05	40	9	40	.09	18.11x10ֿ ֿ³	0.59x10ֿ ֿ³
06	50	15	50	.15	22.63x10ֿ ֿ³	0.98x10ֿ ֿ³
07	60	18	60	.18	27.16x10ֿ ֿ³	1.18x10ֿ ֿ³
08	70	22	70	.22	31.69x10ֿ ֿ³	1.44x10ֿ ֿ³
09	80	26	80	.26	36.22x10ֿ ֿ³	1.70x10ֿ ֿ³
10	90	30	90	.30	40.74x10ֿ ֿ³	1.96x10ֿ ֿ³
11	100	60	100	.60	45.27x10ֿ ֿ³	3.92x10ֿ ֿ³
12	Average		50	0.18	22.63x10ֿ ֿ³	1.18x10ֿ ֿ³

Sample Calculations:

01.Proportional Limit =  .60x 10ֿ ֿ³ KN/mm²

02.Modulus of elasticity = 19.18 KN/mm²

03.Modulus of resilience =

04.Young Strength of offset method = 0.05

05.Proof strength =  46.27x10ֿ ֿ³ KN/mm²

06.Ultimate Strength =  54.32x10ֿ ֿ³ KN/mm²