Improved Self-Piercing Rivet Die and Associated Methods

A die for a self-piercing rivet system includes an upper surface and a cavity. The cavity includes a sidewall surface and a bottom surface. The die includes at least one of a groove on the upper surface that at least partially surrounds the cavity, a rib on the sidewall surface and extending along the sidewall surface within the cavity, or a rib on the bottom surface and extending along the bottom surface within the cavity

Sliding wear analysis of cobalt based alloys in nuclear reactor conditions

The study of the wear behaviour of cobalt based alloys in nuclear reactor environmental conditions is the focus of this work. The alloys are used in components within reactors due to their excellent wear and corrosion resistance and their high hardness in the high pressure and temperature water facing environment. In the nuclear reactor core, cobalt is irradiated producing a highly penetrative gamma emitting isotope, cobalt 60 from stable cobalt 59. Wear of the cobalt alloys, producing wear debris, exacerbates this problem as it may be transported and deposited at various locations throughout the primary loop increasing the potential of radiation exposure. Removing this problem will require the removal of cobalt from the system. In order for suitable replacement materials to be identified, a better understanding of the behaviour of these alloys in the prototypical working conditions must be obtained. This work focuses on two cobalt based alloys used in the ball and race components of rolling element bearings in the reactor core, Stellite 20 and Haynes 25, respectively. The sliding wear behaviour of the alloys in an environment designed to replicate reactor conditions is examined using a bespoke pin on disc tribometer. Wear measurement and microstructural and compositional analysis of the samples tested over a range of conditions are presented and discussed. Concurrent to the experimental work is the development of a wear prediction model using a semi analytical method. The model employs Archard’s wear law as the method of predicting wear using data obtained through experimentation. The accuracy of the semi analytical model is limited however it does give a good estimation for maximum wear depth of the test specimens

Development of a new mechano-chemical model in boundary lubrication

A newly developed tribochemical model based on thermodynamics of interfaces and kinetics of tribochemical reactions is implemented in a contact mechanics simulation and the results are validated against experimental results. The model considers both mechanical and thermal activation of tribochemical reactions instead of former thermal activation theories. The model considers tribofilm removal and is able to capture the tribofilm behaviour during the experiment. The aim of this work is to implement tribochemistry into deterministic modelling of boundary lubrication and study the effect of tribofilms in reducing friction or wear. A new contact mechanics model considering normal and tangential forces in boundary lubrication is developed for two real rough steel surfaces. The model is developed for real tribological systems and is flexible to different laboratory experiments. Tribochemistry (e.g. tribofilm formation and removal) and also mechanical properties are considered in this model. The amount of wear is calculated using a modified Archard’s wear equation accounting for local tribofilm thickness and its mechanical properties. This model can be used for monitoring the tribofilm growth on rough surfaces and also the real time surface roughness as well as changes in the λ ratio. This model enables the observation of in-situ tribofilm thickness and surface coverage and helps in better understanding the real mechanisms of wear

Aluminum Cans for Slushed Beverages and Methods of Making Slushed Beverages in Aluminum Cans

Described herein are aluminum alloy products for slushed beverages and methods of making slushed beverages in aluminum beverages cans. In some examples, an aluminum beverage can may comprise an organic coating or a hydrophobic coating to substantially prevent ice formation at the walls of the can body. In some examples, a gas or nucleating particle can be used to form the slushed beverage. In some examples, a method can comprise rotating or vibrating an aluminum beverage can to produce a slushed beverage

Short note on improved integration of mechanical testing in predictive wear models

In this work, a new global increment nano-fretting wear model based on the effective indenter concept has been used and the results were compared with experimental data. A series of DLC coatings with varied mechanical properties was deposited using industrial scale PECVD system and characterised on a low-drift nanomechanical test platform (NanoTest Vantage). 4500. cycle nano-scale fretting measurements have been performed in order to examine the tribological properties of the coatings. A physical analysis of the nanoindentation test enabled the true coating Young's Modulus (E) and the coating yield strength (Y) to be determined. In comparison to the hardness (H) this is the basis for a more generic understanding of the mechanical coating behaviour. This allowed a direct examination of the influence of the variation of Y/. E in the coatings on the observed nano-fretting wear, with the coating with highest Y/. E showing significantly improved resistance to nano-fretting wear. A preliminary evaluation of the stress field evolution during the test and the extraction of wear and fretting parameters provides the opportunity to discuss the effects possibly being dominant within the nano-scale tribo-tests

A Semi-deterministic Wear Model Considering the Effect of Zinc Dialkyl Dithiophosphate Tribofilm

Tribochemistry plays a very important role in the behaviour of systems in tribologically loaded contacts under boundary lubrication conditions. Previous works have mainly reported contact mechanics simulations for capturing the boundary lubrication regime, but the real mechanism in which tribofilms reduce wear is still unclear. In this paper, the wear prediction capabilities of a recently published mechanochemical simulation approach (Ghanbarzadeh et al. in Tribol Int, 2014) are tested. The wear model, which involves a time- and spatially dependent coefficient of wear, was tested for two additive concentrations and three temperatures at different times, and the predictions are validated against experimental results. The experiments were conducted using a mini-traction machine in a sliding/rolling condition, and the spacer layer interferometry method was used to measure the tribofilm thickness. Wear measurements have been taken using a white-light interferometry. Good agreement is seen between simulation and experiment in terms of tribofilm thickness and wear depth predictions

A finite element based technique for simulating sliding wear

ABSTRACT Micro-machines are known to fail prematurely due to excessive wear by virtue of their inherent high operating frequencies and high surface to volume ratio. In order to predict wear and eventually the life-span of such complex systems, several hundreds of thousand operating cycles have to be simulated. Due to the complexity of wear, the existing wear models are insufficient to reliably predict wear based on the material properties and the contact information. As a first step, a technique has been developed which involves post processing of the results from a finite element (FE) contact simulation with a simple wear model to compute wear. The technique can be used to simulate wear in a pin-on-disc set-up in order to improve and verify the wear models

Etude comparative entre la température expérimentale et simulée d’un couple acier-carbure de tungstène animé d’un mouvement de rotation

De toutes les grandeurs physiques, la température est certainement l’une de celles dont la mesure est la plus fréquente, la température détermine en effet de facon décisive les propriétés de la matière, c’est pourquoi, on recherche comme dans l’industrie et les laboratoires, la mesure et le contrôle très strict des températures sont indispensables. Nous avons réalisé deux séries d’essais d’usure d’un couple acier-carbure de tungsténe animé d’un mouvement de rotation. La force normale P est égale à environ 500 et 1000 N respectivement pour la série 1 et 2, la témperature est prise dans l’intervalle [20–200°C] et la vitesse de glissement fixée à v=0.1 m/s. La température indiquée est celle relevée par un capteur inséré au milieu de l’éprouvette de forme conique et à 2mm du contact. Pour chaque température, deux essais ont été effectués sur deux éprouvettes différentes. La longueur de glissement est de L= 90 m. L’ordre de grandeur de la vitesse d’usure est de quelques 10−5 mm3.N−1.m−1. Le coefficient de frottement se situe entre 0.12 et 0.8. L’objectif de ce present travail est de comparer entre la température expérimentale de ce couple acier-carbure de tungstène en mouvement, mesurée au cours de l’essai et celle simulée en fonction du coefficient de frottement et pour recueillir une information supplémentaire plus exactement sur la température au point de contact