Estimation of the compression strength and surface roughness of the as-built SLS components using weibull distribution

Selective laser sintering (SLS) is a process of fabrication of three-dimensional structures by fus- ing powder particles using a guided laser source. The uncertainty in the mechanical properties of the SLS parts fabricated at the same time and with the same process parameters can affect the repeatability of the SLS process. A vast difference in the mechanical properties of the concurrently processed parts can lower the production quality of the batch. Therefore, the param- eters are required to be design based on the most probable outcome of the desired properties. Weibull distribution is one such statistical-based probability distribution method to measure the likelihood of the occurrence of a value of any random variable falling within a particular range of values. Here, the Weibull distribution was used to measure the relative likelihood (90% probability) of the surface roughness and the compressive strength values of the SLS-built polyamide PA2200 components in the given sample space that was obtained from 20 random samples. The results show that the variance in the surface roughness (scan and built plane) and the compressive strength values were in the range of 6–7 μm and around 10 MPa, respectively. Moreover, the surface roughness of the two orthogonal planes with 90% reliability was measured at 14.81 μm (scan plane) and 12.15 μm (built plane). Similarly, the yield strength and the compressive strength with 90% reliability were found 25.87 MPa and 62.64 MPa, respectively.

Investigation of the prediction capability of Yld89 yield criterion for highly anisotropic sheet materials

In the present work, the prediction capability of Yld89 criterion from anisotropic yield func- tions was investigated in the view of the anisotropic behavior of the sheet metals. Investigation was conducted on two highly anisotropic sheet materials: an aluminum alloy (AA2090-T3) and an advanced high strength steel (TRIP 780). The in-plane variation of material anisotropy and normalized yield surface contours were considered in the evaluation of the prediction capability of the criterion. Firstly, the model coefficients were determined according to stress and strain based definitions. Then, the planar variations of the yield stress and plastic strain ratios and normalized yield surface contours of the materials were predicted according to both identification procedures. Finally, the computed results were compared with experiments to evaluate prediction capability of the model. It was observed from the comparisons that the pla- nar variations of the yield stress ratio could successfully predicted by stress based definition, while the variations of the plastic strain ratios in the sheet plane could accurately predicted by strain based definition. Besides, it was determined that elastic region predicted from strain based definition was larger than stress based definition for AA2090-T3, while the predicted elastic region from stress based definition was slightly larger in than that of strain based defi- nition for TRIP 780 material.

Influence of variable cutting surface contact area on the components of cutting forces and accuracy

The article discusses the process of diamond honing of conical holes. The purpose of the article is to identify the dependence of power in the process of cutting and the effect of changing the contact areas of the components of the cutting forces. The experiments were carried out on a developed installation to determine the cutting ability of diamond honing stones. Depen- dences of linear removal of steel 50 and steel 45 on the applied pressure have been established. Based on the data obtained, it can be concluded that if the value of the Py index goes beyond the limits of pure contact, then this leads to the seizure of surfaces and a deterioration in the quality of processing.

Weibull distribution of selective laser melted AlSi10Mg parts for compression testing

Selective laser melting (SLM) is an additive manufacturing process to fabricate three-dimen- sional structures by fusing powder particles using a computer-guided laser source. The SLM process can produce lightweight bespoke designs, having high strength comparable to con- ventional components. However, the developed surface texture and some of the mechanical properties are still sub-standard compared to the conventional components. The process un- certainty can produce inconsistency in parts’ properties, even those prepared concurrently, affecting SLM parts' repeatability and quality. Therefore, designing applications based on the most probable outcome of the desired properties can embrace process uncertainty. Weibull distribution is a statistical-based probability distribution method that measures the likelihood of the values’ occurrence of any random variable falling in a specific set of values. In this study, the Weibull distribution measured the relative likelihood (90% probability) of the compressive yield, and ultimate strength of the SLM prepared AlSi10Mg samples in a given 22 random sample size. The results showed that the compressive yield and ultimate strength fall between 321 MPa to 382 MPa and 665 MPa to 883 MPa.