Abstract:The article presents an analysis of the modification of the toothing of spur gears. The aim of the modification of the profile on the tooth tip is to compensate for the tooth deflection under loading and to improve the conditions of gear operation. Cases of longitudinal toothing modification of a convex-convex (Cv-Cv type) tooth are described, where the tooth is biconvex and the gear teeth are convex-concave (Cv-Cc type). The conditions of mating of modified gears have been analyzed. A method of machining gears by the step-by-step method has been proposed, which can be used in unit machining of large-module gears with an arbitrary profile modification system.
Recent soft tissue studies have reported issues that occur during experimentation, such as the tissue slipping and rupturing during tensile loads, the lack of standard testing procedure and equipment, the necessity for existing laboratory equipment adaptation, etc. To overcome such issues and fulfil the need for the determination of the biomechanical properties of the human gracilis and the superficial third of the quadriceps tendons, 3D printed clamps with metric thread profile-based geometry were developed. The clamps’ geometry consists of a truncated pyramid pattern, which prevents the tendons from slipping and rupturing. The use of the thread application in the design of the clamp could be used in standard clamping development procedures, unlike in previously custom-made clamps. Fused deposition modeling (FDM) was used as a 3D printing technique, together with polylactic acid (PLA), which was used as a material for clamp printing. The design was confirmed and the experiments were conducted by using porcine and human tendons. The findings justify the usage of 3D printing technology for parts manufacturing in the case of tissue testing and establish independence from the existing machine clamp system, since it was possible to print clamps for each prepared specimen and thus reduce the time for experiment setup.
The primary goal of this research is the analysis of the biomechanical performances of most common transplants (distal tendon of m.gracilis and upper third of m.quadriceps femoris) used for the reconstruction of the medial patellofemoral ligament (MPFL). The secondary goal is the comparison of the data obtained from the research with the data available in the literature.The research was conducted on 16 samples of the human tendon, of which there are 8 gracilis tendons and 8 quadriceps tendons. Tensile strength is significantly higher in gracilis tendon (26 MPa -92 MPa) than in quadriceps tendon (30 MPa -44 MPa). The extensibility is significantly higher in the quadriceps tendon (10% -15%) than in the gracilis tendon (13% -17%). Regarding stiffness (N/mm) there are no significant differences between the groups of gracilis and quadriceps tendons. The module of elasticity is significantly higher in gracilis tendon (235 MPa -855 MPa) in comparison to quadriceps tendon (239 MPa -361 MPa).The biomechanical characteristics of the distal surface third of the quadriceps tendon are more favourable than the distal tendon of the gracilis which could prove applicable in operative techniques of reconstruction of the medial patellofemoral ligament when choosing a transplant.
Original scientific paper Linear independent non-projective transformations are used for different types of applications. Direct analytical method for solving the linear transformation of the characteristic equation for industrial robot is proposed. The theoretical basis of the method derives from the classical solutions with symmetries, but the method does not contain formulas with radicals. Automorphisms are divided into set theory and universal algebra. This feature allows us to use this method more efficiently for other engineering tasks. Keywords: Diuedonne symmetries, kinematic scheme, linear transformations, industrial robot, set theory, universal algebra Rješenja karakteristične jednadžbe za eliptične putanje industrijskog robotaIzvorni znanstveni članak Linearne nezavisne neprojektivne transformacije rabe se za različite vrste aplikacija. Predlaže se direktna analitička metoda za rješenje linearne transformacije karakteristične jednadžbe za industrijskog robota. Teorijska osnova metode proizlazi iz klasičnih rješenja sa simetrijama, ali metoda ne sadržava formule s korijenima. Automorfizmi se dijele na teoriju skupova i opću algebru. To nam omogućuje učinkovitiju primjenu te metode za druge tehničke zadatke.
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