FABRICATION PROCESS
CHAPTER 4 METHODOLOGY
4.1 DESIGN & CONSTRUCTION
4.1.1 Three Point Bending Test Machine used
4.1.1.1 THREE POINT BENDING MODULE DESIGN
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CHAPTER 4
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4.1.1.1.1 Base Dimensions
A base was designed using SolidWorks software so that it can hold the other parts of the module in a specific place without any extra modification to the UTM machine. In order to design the base, first the dimensions of the compressive compartment of the UTM machine were measured. As the length between two columns of the compressive compartment of the UTM machine was 155 mm and the width were 85 mm, it was decided to design the base with a length of 152 mm and width of 50 mm. As the maximum height of the compartment was 270 mm, thickness of the base was primarily decided to 12 mm. Lath machining was not required for the base to fit itself to the UTM machine correctly as all it was needed to drill a hole of 7.83 mm, which was the diameter of the bolt that will be inserted in to the base to make it fit tightly to the UTM machine.
Figure 4.1.1.1.1a: Schematic view of Base V.01
Figure 4.1.1.1.1b: Base V.01
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4.1.1.1.2 Problems Faced
Several problems were encountered after finishing the machining of the Base with a length of 152 mm, width of 50 mm and thickness of 10 mm. Problems are given bellow,
1. As the hole was exactly 7.83 mm, the bolt didn’t fit correctly making it impossible to stay tightly to the UTM machine. So, the base was redesigned.
2. Due to the slight change of the final design of the column, the width of the base was changed.
4.1.1.1.3 Adjustment to the Base
It was decided to change the circular hole in to a capsule one. Vertical milling method was used to machine the capsule shaped hole. The main reason for selecting the capsule hole was that, it would enable adjustment of the base to accommodate the two bolts (Given with the UTM machine) should any adjustment of the placing of the base ever occurred. Capsule hole was done 10 mm from the edge of the and with a radius of 8 mm. With the length of 152 mm, width of 50 mm and thickness of 12 mm and with two capsule holes to fit the bolt tightly to the UTM machine base, these were the final dimension of the base which will be holding the other components of the flexural machine till no. 2 problem was faced while designing the column. More on that in the column section.
Figure 4.1.1.1.3a: Schematic view of Base Version Final
Page | 23 Figure 4.1.1.1.3b: 3D view of Base Version Final
4.1.1.2.1 Column dimensions
Total of two columns were decided to be made. A design was made before proceeding to the machining of the column. The main objective of the columns was to hold the composite material or sheet metal in one place and preventing it from sliding back and forth, thus enabling anyone to test the flexural test with ease. Primarily the length of the column was set to 45 mm. width was set to 32 mm and the height was set to 40+16=56 mm in total. The following figures are the early design of the column with the mentioned dimensions. First one, is the front side of the column and second is the top side of the column from a mechanical drawing as well as the 3D view.
Figure 4.1.1.2.1a: Schematic view of Column V.01
Page | 24 Figure 4.1.1.2.1b: Schematic view of Column V.01 (Top View)
Figure 4.1.1.2.1c: 3D View of the Column V.01
4.1.1.2.2 Problems Faced
Several problems were encountered after reviewing the primary design before preceding to the machining phase. Problems are given bellow,
1. There were no hole or clamp was mentioned in the design, as clamp or hole could be used to tighten the column in a specific place on to the designed base.
2. Welding the columns to the designed base will make it difficult to produce composite materials or cutting sheet metals in to various shape, forcing anyone to make the materials using constant dimensions.
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4.1.1.2.3 Adjustment to the Columns
In order to tighten the columns in to specific place to the base two main things were done at a same time.
Base’s width dimension was altered. The width of the base was changed from 50 mm to 35mm.
Column’s dimensions were also altered. The length was changed from 45 mm to 50 mm. The height of the column was changed from 40+16 mm to 40+16+12 mm (12 mm equals to the thickness of the base which will be holding the columns and indenters). Then, a portion of material was removed from the columns with a height of 12 mm and length of 35 mm from the center (17.5 mm on each side) so that it can slide through the base with ease.
After that, a hole was drilled both side of the column in its “leg” so that using Allen key, a screw can be inserted in to each leg to tighten the column to the base.
Figure 4.1.1.2.3a: Schematic view of Column Version Final
Page | 26 Figure 4.1.1.2.3b: 3D view of Column Version Final
Figure 4.1.1.2.3c: Allen Key is in action
4.1.1.3.1 Indenter Dimension
One indenter was needed for making a flexural module. Unlike other parts of the module this part didn’t need any ‘major’ alteration to its design. Indenter is primarily used to make a single bending possible in a three-point bending set up. An indenter was designed and made with a length of 50 mm, width of 32 mm and a height of 40+16 mm.
The height’s edge was rounded with a radius of 5 mm (According to the ASTM D790 Standard). A screw was fitted on to the head of indenter with a diameter of 8 mm so that it can be used to tighten the indenter to the upper side of the UTM machine’s compressive compartment.
Page | 27 Figure 4.1.1.3.1a: Schematic view of Indenter Version Final
Figure 4.1.1.3.1b: 3D view of Indenter Version Final
4.1.1.3.2 Problems Faced
As it was proved to be rather difficult to find the exact match of the already provided screw attached with UTM machine’s own indenter, an application was written to the authority to grant a permission for taking the UTM machine’s own indenter with us and this way it took two hours to find the exact copy of the screw. The main reason for fining the exact copy of the screw in order to prevent the module to harm the surface of the UTM machine by any means and can be fitted without any external force.
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4.1.1.3.3 Adjustment to the Indenter
No adjustment was made at first, to the indenter apart from drilling an 8 mm hole using lathe machine and fitting a screw in it using wrench. After it was decided to use a custom-made external sensor to measure the load from the machine with the help of an Arduino board, a custom-made screw was machined. The sensor that was ordered has two holes at each end. One hole was used to connect the indenter head to its one section of its head using the custom machined screw and another custom machined screw was used to connect the upper head of the screw to the UTM machine itself.
Figure 4.1.1.3.3: Indenter with sensor attached