Physical modelling of tire wear for the analysis of the influence of thermal and frictional effects on vehicle performance

The tire and vehicle setup definition, able to optimise grip performance and thermal working conditions, can make the real difference as for motorsport racing teams, used to deal with relevant wear and degradation phenomena, as for tire makers, requesting for design solutions aimed to obtain enduring and stable tread characteristics, as finally for the development of safety systems, conceived in order to maximise road friction, both for worn and unworn tires. The activity discussed in the paper deals with the analysis of the effects that tire wear induces in vehicle performance, in particular as concerns the consequences that tread removal has on thermal and frictional tire behaviour. The physical modelling of complex tire–road interaction phenomena and the employment of specific simulation tools developed by the Vehicle Dynamics UniNa research group allow to predict the tire temperature local distribution by means of TRT model and the adhesive and hysteretic components of friction, thanks to GrETA model. The cooperation between the cited instruments enables the user to study the modifications that a reduced tread thickness, and consequently a decreased SEL (Strain Energy Loss) and dissipative tread volume, cause on the overall vehicle dynamic performance.

Mechanical Behavior of Super-Elastic Home-Made NiTi Shape Memory Alloy Bar in Tension

An experimental study on mechanical behavior of home-made super-elastic NiTi Shape Memory Alloy (SMA) bar subjected to tension was made. The SMA bar specimen was 8mm in gage diameter and 50mm in gage length. The experimental tests were carried out by applying repeated cyclic loads. The tested tension strain amplitudes were 1%-7% and material phase was austenite. The mechanical characteristic parameters, such as phase transformation stress, deformation module, residual strain, energy loss and equivalent damping were studied. The effects of strain amplitude, loading rate and loading cycles on these parameters were analyzed. The considerable super-elasticity and stable cyclic behaviors of home-made SMA bar during the test showed its great application potential in aseismic devices.

Study on Evaluation Method of Corroded Reinforcing Steel

Corrosion ratio is an important index to study the mechanical deteriorates of the steel bars, which has a significant effect to evaluate the residual bearing capacity of reinforced concrete structures. To investigate the mechanical properties of the corroded steel bars, Strain energy loss as corrosion ratio is firstly proposed. Tensile test are conducted on ribbed and plain steels, which are corroded by acceleration corrosion method. Comparing with the weight loss and cross-section loss to describe the effect of corrosion of reinforcing bar, the strain energy loss of reinforcing bars is calculated by Simpson quadrature. Results from this paper and other researchers’ test suggest that the strain energy loss may be a better parameter than weight loss or section loss which to assess the corroded steel bars.

Strain Energy as a Criterion for Stress Softening in Carbon-Black-Filled Vulcanizates

Stress softening of vulcanizates of SBR 1500 containing different blacks possessing the same “structure” but varying in surface activity, and effects of different black loadings, of black structure levels, and of particle size, were investigated. It was concluded: 1. Strain-energy loss can be used as a quantitative measure of stress softening, and initial strain-energy input as a measure of prestress severity. 2. The effects of carbon black and polymer variables can be normalized in a single general relationship by plotting per cent strain-energy loss as a function of initial strain-energy input for filled vulcanizates. 3. With the exception of natural rubber, gum vulcanizates studied showed no stress softening. The stress softening of natural rubber gum vulcanizates is attributed mainly to stress-crystallization. 4. Stress-softening of filled vulcanizates is not a completely reversible process. Rates of stress recovery are reasonably rapid. 5. The degree of stress softening can be predicted from the initial stress—strain curve, the prestress severity desired, and the general correlation based on strain-energy considerations found in this study. 6. Prestressing reduces abrasion resistance as measured in the laboratory.