The study is focused on three cervical spine ligaments that stabilize the spine and protect the spinal cord – ALL, PLL, LF. Fresh cervical spine specimens were teste d in physiological conditions under tensile loading. An increase trend in failure load, failure stress, stiffness and modulus was observed, but proved not to be significant for all ligament types. The study results indicate the importance of carefully applying the existing experimental data from the literature in numerical modelling.
COBISS.SI-ID: 13527579
Cervical spine ligaments have an important role in providing spinal cord stability and restricting excessive movements. Therefore, it is of great importance to study mechanical properties and model the response of these ligaments. The aim of this study is to characterize ageing effects on failure properties and model damage of three cervical spine ligaments: the anterior and the posterior longitudinal ligament and the ligamentum flavum. A total of 46 samples of human cadaveric ligaments removed within 2448 hours after death have been tested. Uniaxial tension tests along fibre direction were performed in physiological conditions. The results showed that ageing decreased failure properties of all three ligaments (failure load, failure elongation). Furthermore, the reported non-linear response of cervical ligaments has been modelled with a combination of the previously reported hyperelastic and damage model. The model predicted a non-linear response and damage region. Material parameters are in agreement with experimental data, and the quality of agreement is represented with very low RMS error values and the values of coefficient of determination close to 1.
COBISS.SI-ID: 13356827
In this article, the process of deep rolling of the torsion bar for heavy armored vehicles is investigated. Deep rolling is a mechanical process of introducing compressive stresses into near surface regions of the working piece. The main objective of deep rolling of the torsion bar is to increase fatigue strength and life time of the torsion bar. The investigated specimen (quenched and tempered before deep rolling) was deep rolled according to the producer's standard technology procedure. The material used in this study was the TORKA steel, which is a low-alloy steel with high strength and toughness. The material was characterized through a series of monotonic and cyclic tension compression experiments. Parameters used in the process were changed during deep rolling of the specimen and their influence was measured. Residual stresses resulting from the deep rolling process were measured with an X-ray diffraction (XRD) device and evaluated with the use of commercial finite element method software. An isotropic and kinematic hardening material model based on the cyclic characteristics of the material was used in three dimensional simulation of deep rolling. Numerical simulation results agree very well with the results obtained from XRD measurements.
COBISS.SI-ID: 13818651
The Multi Material Arbitrary Lagrange Euler (MMALE) method is widely used method for numerical investigation of structural response under blast loading. However the method is very demanding for use at the other hand. In this paper are presented the results of the detailed numerical investigation in order to simplify some decisions contributing to the accuracy and efficiency of this model. The influence of mesh properties (particularly mesh size, its biasing and distance of the boundary conditions from the deforming structure) on blast wave loading parameters and structural response is investigated in detail and based on the results minimum mesh design criteria is proposed. The results obtained are presented as a function of the scaled distance and additionally related to the radius of the charge. Validation studies were also done successfully.
COBISS.SI-ID: 13718555
Material failure is most often caused by cyclic fatigue loading. Prior to failure, material damage growth can be observed by means of various methods. Through experimental research, it has been determined that individual methods are appropriate only for specific types of materials and that analysis results also depend on the method of material loading.Therefore, a question is being raised on which method to choose for a specific material andmethod of loading. For this purpose, the paper presents the results of the damage initiation process and damage growth for high yield strength material Armox 500T, as well as forannealed low yield strength steel 42CrMo4. The measured data on material response areevaluated by means of three different methods which are based on the elastic modulus,plastic strain energy, and maximum stress.Parameters and damage values were obtained from the measurement data by meansof various damage evaluation methods. After that, an overview was made of the differences between these methods. The results were used to determine the deficiencies and benefits of each method and the most appropriate method for subsequent tests was selected. The most frequently applied damage identification method, i.e. the elastic modulus method, proves to be in appropriate for high yield strength materials.
COBISS.SI-ID: 13258523