Fatigue strength of inner knurled interference fit joined by forming and cutting methods

The joining of machine parts by plastic forming is a common method for transmitting forces and torque. In drive trains, the ‘knurled interference fit’ has a high transmission capacity through the combination of frictional connection and form fit. In the present study, the shaft specimen made of C45 steel material is joined with an inner knurled hub made of 16MnCr5 case hardened steel. The influence of the joining process parameters on the torsional fatigue strength of the shaft-hub connection is investigated by means of experimental studies. The most important parameter is the chamfer angle of the knurled hub, which determines the rate of strain hardening in the material and differs between the cutting and forming joining processes. This study shows that knurled interference fit connections joined by forming achieve a higher fatigue strength and a higher maximum static torque than connections joined by cutting

Blockchain-Based Sustainable Retail Loyalty Program

This paper addresses the issue of sustainability in retail sales, where the composition of the products themselves, their production and packaging process, and their transport to the point of sale play an important role. We propose a solution to apply a unified system of environmental product rating in different retail chains where trust is ensured through a distributed ledger. The system allows fair and transparent rewards for customers who purchase eco-friendly products while also maintaining their privacy. The prototype of the decentralized application for the uniform loyalty system based on the Algorand blockchain has shown promising results in terms of throughput and cost efficiency. We believe that the prototype has the potential to revolutionize loyalty systems and promote sustainable practices. This study provides key insights into how to interconnect retailers and customers into a uniform reward program, how to motivate customers to purchase sustainable and eco-friendly goods, and how retailers can manage the amount of reward for the given Eco-score categories

Evaluation of the Immunogenicity of a Vascular Graft Covered with Collagen Derived from the European Carp (Cyprinus carpio) and Bovine Collagen

Aim. To assess the systemic and local immunological response to subcutaneous implants of a vascular graft covered with collagen extracted from the European carp (freshwater fish) or with collagen of bovine origin. Methods. Pieces of a vascular graft covered by pure bovine (Bos taurus, BOV, n=14) or carp (Cyprinus carpio, CYP, n=14) collagen 5 mm in size were implanted subcutaneously in the dorsum of a Balb/cOla mice. A sham operation group of 12 animals served as the control. At 7 and 14 days after the operation, one-half of each group was terminated and blood for serum, spleen, and implant with surrounding tissue were collected. Mean cytokine (TNF-α, IL-10, IL-4, IL-1β, IL-13, and IFN-γ) levels in serum were determined using ELISA. Spleen cell cultures were used for in vitro testing of lymphocyte proliferation and cytokine secretion. Local expressions of IL-6, IL-10, TNF-α, TGF-β, CCL-2, and CCL-3 were determined using PCR. Results. We found no significant difference among control, BOV, and CYP groups in mean cytokine serum levels at seven days. At day 14, the BOV group had higher levels of TNF-α (P=.018) and both the BOV and CYP groups had lower levels of IL-4 (P=.011 and P=.047, respectively) compared with the control group. Both tested implants showed only a minimal effect on the production of selected cytokines. Cell proliferation in the CYP group stimulated by CYP gel at 14 days was significantly lower than by BOV gel in BOV group (P=.0031) or by CYP gel in the control group (P=.041). The difference between the groups in the local RNA expression of all the tested mediators both at 7 and at 14 days was not significant apart from a lower level of TNF-α in the BOV group compared to CYP at 14 days (P=.013). Conclusions. Implants covered with carp collagen induce an immunological response that is comparable to that of bovine collagen covered implants in a mouse model