Coupon Test Report

Coupon test report

LIU, WEI-YI
registration number: 160108260
Date: 03/11/2016

Introduction

The coupon test experiment is set to compare the steel-steel and aluminium-steel plate weld joints regarding their strength and stiffness. The primary values can be obtained through statistical analysis from different groups to avoid sampling errors.

The results can, therefore, be used to decide the strut material and the number of weld points to fit the design specification.

Procedure

The experiment starts with marking welding points on the steel and aluminium rolled tubes as the drawing provided, followed by having them welded on separate sheet metal under the operation of respective spot welders. Each group, then, has their both coupons gripped on the tensometer machine for testing its tensile behaviour. The measured raw data, force over deflection, can be plotted in the graph to find out each coupon’s main characteristics – Maximum Force until failure (Fmax), Limit of Proportionality (Flim), Maximum Deflection before failure (Dmax) and Stiffness. These data collected from each group can, therefore, be clean up and then derived into the final results, Fmax or Flim, in the assumption of normal distribution for the design specification.

Results

As shown in Table 1 and 2, each table contains the group data derived from the testing on Steel coupon and Aluminium coupon. To avoid sampling errors in the final results, statistical analysis is carried out by removing outliers in the data. Therefore, any data outside the range of one standard deviation from the mean value, highlighted in red colour, should be eliminated according to Table 3 and 4. While one of the design specification is no more than 5mm beam displacement under maximum load, the Flim (limit of proportionality) is only the suitable value for both end-fitting designs. The final statistical results of this value for both end-fittings are listed in Table 5.

Table 1. Tensile test on Aluminium-steel coupon