Desirability Function Analysis (DFA) in Multiple Responses Optimization of Abrasive Water Jet Cutting Process

This paper introduces optimization of machining parameters for high-pressure abrasive water jet cutting of Hardox 500 steel utilizing desirability function analysis (DFA). The tests were carried out according to the orthogonal matrix (Taguchi) L9. The control parameters of the process such as pressure, abrasive flow rate, and traverse speed was optimized under multi-response conditions namely cutting depth and surface roughness. The optimal set of control parameters was established on the basis of the composite desirability value obtained from desirability function analysis and the significance of these parameters was determined by analysis of variance (ANOVA). The effects show that optimal sets for high cutting depth and small surface roughness is high pressure, middle abrasive flow rate, and small traverse speed. A confirmation test was also leaded to validate the test results. Results of the research have shown that machining efficiency at keeping good level quality of cut surface can be improved this approach.

Analyses of Vibration Signals Generated in W. Nr. 1.0038 Steel during Abrasive Water Jet Cutting Aimed to Process Control

The presented research was aimed at finding a suitable tool and procedure for monitoring undercuts or other problems such as cutting without abrasive or inappropriate parameters of the jet during the abrasive water jet (AWJ) cutting of hard-machined materials. Plates of structural steel RSt 37-2 of different thickness were cut through by AWJ with such traverse speeds that cuts of various qualities were obtained. Vibrations of the workpiece were monitored by three accelerometers mounted on the workpiece by a special block that was designed for this purpose. After detecting and recording vibration signals through the National Instruments (NI) program Signal Express, we processed this data by means of the LabVIEW Sound and Vibration Toolkit. Statistical evaluation of data was performed, and RMS was identified as the parameter most suitable for online vibration monitoring. We focus on the analysis of the relationship between the RMS and traverse speed.

A COMPARATIVE ANALYSIS OF MACHINING PARAMETERS INFLUENCE ON ACCURACY AND ROUGHNESS IN WATERJET AND LASER CUTTING

The paper presents a comparative analysis of the technique of cutting materials such as water jet cutting and laser cutting. The tests were carried out while cutting plastic elements, such as: PMMA, HIPS and ABS. To compare the analysed cutting methods, it was necessary to limit the type of material to be cut to the selected plastics due to the limited thickness range of the samples cut with the use of the laser used for the tests. The workpiece was designed in AutoCAD. The geometry was designed in such a way that it was possible to compare the accuracy of cutting both straight sections, curves and holes using the cutting techniques tested. The roughness of the treated surfaces (edges of the samples) was also analysed. A roughness gauge was used to test the edges. The obtained research results were compiled and analysed to determine the optimal technology and parameters of cutting processes for individual types of selected materials and shapes. As it was shown, the wrong selection of the cutting technology in relation to the processed material or the wrong selection of machining parameters may lead to the destruction of the detail being made and incur significant costs.

Experimental Approach for the Failure Mode of Small Laminated Rubber Bearings for Seismic Isolation of Nuclear Components

Response characteristics of small-sized laminated rubber bearings (LRBs) with partial damage and total failure were investigated. For nuclear component seismic isolation, ultimate response characteristics are mainly reviewed using a beyond design basis earthquake (BDBE). Static tests, 3D shaking table tests, and verification analyses were performed using optional LRB design prototypes. During the static test, the hysteresis curve behavior from buckling to potential damage was observed by applying excessive shear deformation. The damaged rubber surface of the laminated section inside the LRB was checked through water jet cutting. A stress review by response spectrum analysis was performed to simulate the dynamic tests and predict seismic inputs’ intensity level that triggers LRB damage. Shaking table tests were executed to determine seismic response characteristics with partial damage and to confirm the stability of the superstructure when the supporting LRBs completely fail. Shear buckling in LRBs by high levels of BDBE may be quickly initiated via partial damage or total failure by the addition of torsional or rotational behavior caused by a change in the dynamic characteristics. Furthermore, the maximum seismic displacement can be limited within the range of the design interface due to the successive slip behavior, even during total LRB failure.

Water Jet Automation

Water jet cutting has been an extremely helpful tool that creates flawless parts with tolerances up to 0.1 mm. During the cutting process, it is important to note that each step must be optimized to create the best finish or maintain the correct tolerance zone. These steps are composed of abrasive mass flow rate, traverse speed, and standoff distance. In order for these optimization techniques to be followed a strict set of rules must be followed to ensure consistent progression. Programs such as MATLAB can be utilized to reduce human error in the calculations. MATLAB files can then be saved to use with other materials and thickness combinations.

Effect of Steel-Cutting Technology on Fatigue Strength of Steel Structures: Tests and Analyses

This paper presents the results of comparative fatigue tests carried out on steel S355J2N specimens cut out using different cutting methods, i.e., plasma cutting, water jet cutting, and oxyacetylene cutting. All the specimens were subjected to cyclic loading from which appropriate S-N curves were obtained. Furthermore, face-of-cut hardness and roughness measurements were carried out to determine the effect of the cutting method on the fatigue strength of the tested steel. The fatigue strength results were compared with the standard S-N fatigue curves. The fatigue strength of the specimens cut out with oxyacetylene was found to be higher than that of the specimens cut out with plasma even though the surface roughness after cutting with plasma was smaller than in the case of the other cutting technology. This was due to the significant effect of material hardening in the heat-affected zones. The test results indicate that, in comparison with the effect of the cutting technology, the surface condition of the specimens has a relatively small effect on their fatigue strength.

3D EVALUATION OF THE TOPOGRAPHY OF THE SURFACE BY ABRASIVE WATER JET MACHINING TECHNOLOGY

The article deals with contact and non-contact evaluation of surface roughness created by water jet cutting technology (AWJ). Non-contact surface measurement was performed using an LPM laser profilometer. The values measured by the laser profilometry method were compared with the values measured by the contact method, the Mitutoyo SJ 400 roughness meter. Six samples were produced. Three in stainless steel and three in structural steel. In order to achieve a different surface topography, different feed rates of the cutting head were used on the samples, which was reflected in the quality of the resulting surface. The evaluated parameters were the average arithmetic deviation of the assessed profile and the largest height of the profile inequality.