The number of bends is compared to the number of the fracture of the test specimen after conducting the bend test. The greater the number, the higher the ductility of this material. The ductility ratio defines the total deflection at the elastic limit. By seeing the provided graph it can be understood that the ductility ratio is
Elongation (%) = 100 x ?L/Lo
Reduction of the C.A area (%) = 100 x (Ao – Af)/Ao
Both of the value is given in percentage and show the value of the ductility index. After observing the graph and the table, the ductility ratio is 2.225.
The toughness of a material basically is a fundamental property of the material that absorbs energy and withstands fracture. The amount of the energy that is imposed per unit volume that a material can absorb before rupture or any fracture which leads to the failure of the material.
Comparison between the behavior of metal in tension and timber in flexure
There are a lot of similarities and dissimilarities in the behavior of tension in meal and the flexure in timber. A lot of attributes of the material of metal and timber define the changes in behavior after applying the load. The failure and the mechanism of failure of both materials are the main attributes that differentiate each other (Xia et al. 2021). Along with these, the initial stiffness, the bearing capacity, and the ductile nature of these materials are the nature of the failure. In scenarios of the timber section, the failure that is observed is the brittle shear failure that occurred along with the grain. But for the metal scenarios, the failure occurs in the bottom flange as the load is uniformly distributed to the whole body (Wang and Yan, 2019). The metal has the capacity to resist the tensile load by bending its shape against the applied load. That is why for reinforcement purposes in the concrete beam, steel is used to provide the tensile strength. On the other hand timber does not provide as tensile strength as metal. It can hold some amount of load by bending its shape but due to the nature of the material, the shear failure can be observed at the timber body (Chen et al. 2021). Another component is the ductile nature of the material. For the timber section the ductile nature defines the shape of the failure that happened along with the grain. It is same for the metal body, for its ductile nature, it provides more stiffness. This phenomenon leads to resist more strength than the timber body.
From the provided table it can be seen that the load associated with yielding is = 8.5 KN
Calculation of the load associated with load bearing capacity
The load that associated with the load bearing capacity is Qf = Su × Ncu + Qo [Ncu = Nc.sc.dc]
= 78 kPa
Description of the behavior of the beam up to failure
From the given table of provided load and deflection reading, it can be understood that the behavior of the failure of the beam would be bending failure. As the timber beam is simply supported and the load provide on it would be distributed uniformly.
Figure 1: Load deflection curve
By seeing the load deflection curve it can be said that the sagging moment is occurred in the timber beam. The dead load and live load occurred on it distributed uniformly to the whole body. The tension force applied on the bottom part. As soon as it reaches the yields limit of the material, the failure happened in the timber beam. [Refer to Appendix 1]
Description of the energy absorbed by the specimen up to failure
The table that is given can provided the records of the loads that occurred on the timber beam. It seems that the load are provided till the capacity limit of the beam. At the highest load provided to it, the timber beam seems to have reached its highest capacity of load resisting. The shear failure cannot be happened in that case as the supports are given to the beam is simply supported. That is why the tension failure occurred as the bottom part of the beam was experiencing sagging moment.
Therefore the energy absorption: My+ Øy (µØ - 12)
= 2923.33
Comparison of load-displacement curve with other groups` curves via plotting them all in one graph
Figure 2: Load-displacement curve
The given figure is showing the load displacement curve plotted of the timber beam under flexure. The values are from the various groups and the task is to do the comparison among the curves. It can be clearly seen that the most displacement happened in the timber beam of group 8. In terms of resisting load, the timber beam sample of group 2 has resisted the most amount of load with the second highest displacement. The curve of the main group is showing that the value of the displacement of the sample timber beam is approximately 10.4 mm and the highest load that resisted is approximate 8 KN. The sample of the main group has the third lowest amount of displacement, which is followed by the sample of group 7 who has the displacement of approximate 10.5 mm. The lowest displacement occurred in the sample of group 4 who has the approximate displacement of 9 mm. The potential reasons for these differences are might be the quality of the material. Although timber is used in the test of every group, but the quality of the timber vary with each other and that is a reason for the differences. The second is the differences in the seasoning of the timber that are used for testing. Every material has its own seasoning quality, the load resisting capacity of the timber is based on it. That is why the load resisted by every sample is different from the others which is caused by the seasoning quality of material.
Testing Of Concrete Under Compression
Discussion of how the water/cement ratio affects the axial compression resistance of concrete
The water/cement ratio is determined at the time of preparing the mix designing process of the concrete. There are many forms of concrete which depends on the ultimate strength of that particular concrete. For example there are M20, M25 which characterizes the concrete. M25 concrete means it gives minimum 25 MPa strength that can be getable after 28 days of proper curing of concrete. The whole mix design depends on the ratio of the water/cement of that particular concrete (Shi et al. 2021). The amount of cement, sand and other components vary based on the value of water/cement ratio. The strength of that particular concrete generally increases with the time and the ratio of water and cement mentioned in the mix design (Stach et al. 2021). The increase in the ratio of the water and cement leads to the decrease in the amount of the coarse aggregates and the fine aggregates of that concrete mix design.
Discussion of the effect of time on the axial compression resistance
By looking at the provided dataset for every water/cement ratio, there are lot of things to discuss about the results. It is clearly understandable by looking the table that reduction of the water/cement ratio, the strength obtained by that particular concrete is increasing continuously. For the first case the water/cement ratio of the concrete was 0.5. The concrete gives the compressive strength after 28 days is 35 MPa. For the second case the water/cement ratio was 0.4 and the compressive strength after 28 days was 46, which is higher than the first scenario (Chen et al. 2021). For the next scenario the water/cement ratio was 0.3 and the compressive strength was 57 MPa. For the last scenario, the water/cement ratio was 0.25 and the compressive strength was 65 MPa which is the highest among the four cases.
It can be clearly understood that the strength of that particular concrete is increases with the decrease of the water/cement ratio (Zhou et al. 2019). There are several potential reasons for this phenomenon. For first reasons it can be said that, the amount of the coarse aggregate increases with the reduction of the water/cement ratio. This means the mix design holds more coarse aggregate which has the lower water/cement ratio (Jiang and Liu, 2019). Stone chips of 20mm and 10 mm falls in the categories of coarse aggregate. The coarse is the second in terms of giving strength to concrete after cement. That means the concrete with more coarse aggregate will provide more strength compared to the other concrete (Islam, 2020). Another reason for this phenomenon is that increase in water cement ration means that there are less water provided in the mix design which increases the amount of cement. Less water content in mix design means more strength of the concrete as the excess water in concrete reduce the strength.
Prediction of the axial compression resistance for each W/C ratio corresponding to day 5, day 10 and day 20.
For Water/cement ratio: 0.5
Figure 3: Compressive strength curve for W/C 0.5
The predicted compressive strength after 5 days is = 22 MPa
The predicted compressive strength after 10 days is = 28 MPa
The predicted compressive strength after 20 days is = 33 MPa
For Water/cement ratio: 0.4
Figure 4: Compressive strength curve for W/C 0.4
The predicted compressive strength after 5 days is = 36 MPa
The predicted compressive strength after 10 days is = 41.5 MPa
The predicted compressive strength after 20 days is = 44 MPa
For Water/cement ratio: 0.3
Figure 5: Compressive strength curve for W/C 0.3
The predicted compressive strength after 5 days is = 48 MPa
The predicted compressive strength after 10 days is = 53 MPa
The predicted compressive strength after 20 days is = 56.5 MPa
For Water/cement ratio: 0.25
Figure 6: Compressive strength curve for W/C 0.25
The predicted compressive strength after 5 days is = 57.5 MPa
The predicted compressive strength after 10 days is = 61 MPa
The predicted compressive strength after 20 days is = 64 MPa
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