Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, the scientific journal of the Mendel University in Brno, Czech Republic

The paper deals with the actual topic of mechanical properties of 3D prints made from the polymer material rPET-G and its changes. Using this material in additive technology has great potential in the automotive industry. The research evaluates five different post-processing modifications of 3D prints from rPET-G (recycled polyethylene terephthalate-glycol) material produced by the Fused Filament Fabrication technology. The post-processing included the chemical smoothing of the samples using dichloromethane vapors and heat treatment in an annealing furnace. An epoxy resin, a synthetic coating, and a water-based coating were also applied. The standard was represented by samples without post-processing modifications, both in the form of recycled material and in the form of virgin PET-G. The texture of the samples was evaluated according to EN ISO 4287. Furthermore, the moisture absorption of the samples was evaluated using the gravimetric method according to EN ISO 62. The mechanical testing of the samples was carried out using a tensile test (EN ISO 527-2), a three-point bending test (EN ISO 178), impact strength (EN ISO 179-2), and a cupping test (EN ISO 1520). Degradation of the coatings took place using cyclic tests, which used a combination of exposure in a salt fog environment and in a climate chamber. The results of the experiments indicate that heat treatment appears to be a universal post-processing technology, as this method statistically improves not only the mechanical properties but also significantly reduces moisture absorption.

Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, the scientific journal of the Mendel University in Brno, Czech Republic

This work is aimed on influence of diesel engine parameters that is used with mixture of gas and diesel fuel. The first part of the article describes diesel fuel systems where small part of diesel fuel is replaced by LPG or CNG fuel. These systems are often called as Diesel-Gas systems. Next part of the article focuses on tested car and measurement equipment. Measurement was performed by common-rail diesel engine in Fiat Doblň. Tests were carried out in laboratories of the Department of Engineering and Automobile Transport at the Mendel University in Brno. They were observed changes between emissions of used fuels – diesel without addition of gas, diesel + LPG and diesel + CNG mixture. It was found that that the addition of gas had positive effect on the performance parameters and emissions.

This article deals with the verification of relations between the electric current of engine starter and tightness of the combustion chamber and the possibility of its use for the evaluation of the state in terms of engine wear. Engine wear is closely related to the quality of fuel combustion and also with the amount of produced harmful emissions. On this basis, it would be possible to extend the technical requirements of the protocol OBD to include the indirect control of engine wear. To meet the objectives set out above measurement was carried out by a petrol engine, which was located in the vehicle Škoda Felicia Combi GLX 1.3 The whole measurement was divided into several parts. The first measurement was carried out on the abovementioned motor without simulating leakage. The second measurement was performed when the leakage of one cylinder was simulated. Simulated leakage was conducted at removing the spark plugs. Other measurements simulated “mild” leak of the whole engine – all cylinders. Leakage was implemented by loosing all the spark plugs about 8 turns against full tightening with the appropriate torque. The last, fourth measurement simulates a “large” leaks of engine cylinders. This leakage was induced by removing all the spark plugs from all cylinders. As the measurement results showed leakage of one cylinder, and also the whole engine is reflected not only in the individual amplitude of the starter current, but also the shape of the entire curve.