## 2 Experimental Details
### Experimental Procedures
#### 2.3.3 RJS Strength Degradation Analysis  
The RJS specimens were used to determine the effect of several ageing conditions described below. The specimens were then shear tested and compared with their unaged counterparts, as a benchmark. For each condition, a minimum of three valid specimens were tested. Ageing Due to Common Industrial Fluids  
In order to simulate the saturation time of the adhesive joints for this portion of the analysis, RJS specimens were immersed in water and cutting emulsion for one month. Because, in the case of the milling tools under study, it is uncommon to undergo more than five/six sharpening cycles, two dielectric fluid exposure conditions were tested for each of the specimen materials, corresponding to the time of one tool sharpening cycle (200 min) and five sharpening cycles (1000 min). For each fluid, both steel and aluminium specimens were aged. Ageing Due to Surface Coatings  
To evaluate the effect of common industry surface coatings on the strength of the adhesive joint, a set of steel RJS specimens was subjected to oxidation and nickel-plating procedures. These treatments were applied by FREZITE(r), following the same surface coatings used in current commercial milling tools. Oxidation and nickel-plating are treatments that subject the workpiece to chemical baths at high temperatures and, therefore, are expected to cause a severe degree of hygothermal degradation of the adhesive joint. Ageing Due to Tool Cleaning  
To simulate tool cleaning, two procedures are defined, a continuous process reproducing long exposures and a cyclic process to reproduce multiple cleaning cycles. For the first case, the RJS specimens were once again continuously submerged, but in this case in petroleum oil and ultrasound fluid. After a given period of time, a group of specimens was taken out of the fluid and was subjected to shear strength testing. By observing how shear strength changes with immersion duration, it was possible to provide a more accurate estimate of the maximum time a tool should be in contact with the cleaning fluid. Then, as mentioned previously, in order to evaluate the effect of cyclic exposure to the fluids, RJS specimens were immersed for a certain time span before being dried in the oven, while placed in silica, at 70 \({}^{\circ}\)C for 45 min. This was done to simulate cutting operations at an elevated temperature. This cycle was repeated six times to simulate the maximum number of sharpening cycles. By doing this, we can confirm how the tool works after being cleaned several times by obtaining the adhesive joint behaviour after a number of cleaning cycles. The time spans of both the continuous and cyclic procedures were longer for the petroleum oil, since the ultrasound fluid is more damaging. Figure 3 displays the ageing plan for both fluids and presents the times spans used for each. Sandblasting was also considered, as it is a simple and effective method for removing initial residue from the tool. Four different time periods were applied to the RJS specimens--10, 35, 70, and 150 s. This allows for the determination of the maximum amount of exposure time for which this technique is practical. Additionally, the data supplied by the manufacturer are shown in Table 3, showing adhesive ageing as a result of exposure to two types of fluids--petroleum-based fluids and ultrasound fluids. This was used as a benchmark against the results from the current tests. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Medium** & \(P_{aged}\) @ **100 h/\%** & \(P_{aged}\) @ **500 h/\%** & \(P_{aged}\) @ **1000 h/\%** \\ \hline
**ATF gear oil** & 85 & 85 & 75 \\
**Diesel** & 83 & 82 & 80 \\
**Motor oil 10W40** & 96 & 95 & 95 \\ \hline
**Ethanol** & 90 & 72 & 40 \\
**Water/glycol** & 87 & 86 & 80 \\
**Benzine** & 81 & 80 & 72 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Ageing guidelines for different mediums, based on the compression shear strength of aluminium single lap joints of aged specimens against unaged specimens. Obtained from the adhesive’s datasheet.