Conventional Mechanical Testing Research Articles

Performance of dental biomaterials: Conference report

On August 13–18, 1989, a dental conference, entitled “Dental Biomaterials: Assessment of Performance Based on Engineering and Statistical Methods”, was held in Santa Barbara, California. This conference was sponsored by the Engineering Foundation with co-sponsorship by the United States Army Institute of Dental Research, the United States Naval Dental Research Institute, Block Drug Co., Dentsply International, and the National Institute of Standards and Technology. The objective of this conference was to explore engineering and statistical methods for assessing the resistance of dental biomaterials to structural degradation and failure and for predicting the relative reliability of dental restorations and prostheses under clinical conditions. The conference was designed to evaluate the merits of established and new technology relative to the performance of dental materials. Analytical and experimental methods included fracture mechanics, conventional mechanical tests, adhesion tests, fractographic analysis, finite element analysis, statistical analysis, tribology, image analysis, x-ray diffraction, and scanning tunneling microscopy. The central theme was the development of a systematic approach to predict material performance under clinical conditions based on stress analysis, correlation of clinical data with in vitro data, and fracture surface characterization based on qualitative and quantitative methods. Supported in part by NIDR Grant No. DE06672.

Aluminum quality breakthrough for aircraft structural reliability

In 1983, Alcoa's Davenport Works initiated a statistically designed experiment to evaluate effects of processing on thick plate metal quality. An outgrowth of this program is a breakthrough in quality and resultant property improvements that can be exploited for fatigue and fracture-critical structures. This paper describes the statistical quality control effort, and gives evidence of the improved capabilities typical of recently produced high-quality material. Among conventional mechanical property tests, the smooth fatigue test is shown to be the most discriminating for initial metal quality. Data are shown correlating longer lifetimes to reduced microporosity size in the improved plate. Replicate fatigue tests enable definition of a characteristic initial flaw size distribution that can serve as a starting point for flaw growth analysis and life management. These findings are discussed relative to initial fatigue quality guarantees and compatibility with emerging U.S. Air Force durability analysis methodology. In summary, it is shown that the combination of more discriminating testing and a superior product offers considerable promise for reliability improvement in aircraft structural designs of the future.

Voltage contrast electron beam testing experiments on very large scale integrated chip packaging substrates

Test and inspection are key in reducing costs and increasing reliability of multichip hybrid modules. Increasing very large scale integrated chip packaging densities requiring finer linewidths and more substrate interconnection networks are taxing the probing resolution, throughput, and reliability of conventional mechanical probe test systems. Voltage contrast electron beam test technology was seen as an attractive alternative for high-throughput, noncontact testing of unpopulated packaging substrates and high-density printed wiring boards. A conventional scanning electron microscope was modified by adding large-field vector deflection, a large-field secondary analyzer, beam blanking, an electron flood gun, and a computer control system, thereby providing the primary test functions required for opens and shorts testing: net charging, net voltage measurement, and global charge removal. Successful substrate test results are shown along with data which highlight potential failure mechanisms such as substrate material variations, charge leakages, and contaminants.

The Effect of Carburization in Sodium on the Mechanical Properties of Austenitic Stainless Steels

Conventional mechanical properties tests (tensile, stress/rupture, and impact toughness) have been performed on annealed specimens of austenitic stainless steels (0.152 cm thick, 0.635 cm wide) which have been carburized in high temperature (538–593°C) sodium for times up to 2000 hr. Included in the work were alloys which might have been more resistant to carburization than conventional alloys, Type 310SS, 18-8-2, Uranus-S and Inconel-601. Results indicate that the tensile and stress rupture ductility of all the alloys decreased to less than 5 percent in tests at 538–593°C when the bulk carbon content of the specimens was 0.4 percent or greater. The decrease in ductility of surface-carburized specimens is much greater than that of alloys of the same nominal composition and same bulk carbon content but with the carbides homogeneously distributed throughout the specimen. It is shown that the brittle surface layer fractures in a transgranular, cleavage mode while the center of the specimens fail in the normal shear mode.

Correlation of Transient-Test Data with Conventional Mechanical Properties Data

AbstractThermal transient-test failure data for proto-typic fast test reactor fuel cladding were correlated with failure data from conventional mechanical properties tests. The correlation was developed by the application of a life fraction rule to stress rupture, tensile and tube burst, as well as transient test data and by constructing a Larson-Miller plot which encompasses the stress and temperature range for all four types of tests. The high degree of correlation between the different types of test data indicates that this approach will be useful in the prediction of failures under hypothetical transient conditions. It is shown that the Dorn parameter can be used instead of the Larson-Miller parameter with equal success for the various types of mechanical properties tests.

鋼材の破壊靭性値と引張および衝撃性質との関係

The method for determining the notch toughness KIC from the results of the conventional mechanical tests with small specimens was studied. The following correlation was found between the notch toughness KIC and the tensile and impact properties:(This article is not displayable. Please see full text pdf.) \ oindentwhere k is a non-dimensional constant, σT a true fracture stress, ICP a Charpy impact value and E is Young’s modulus.The analysis of the published data by the above equation revealed that those data showed different tendencies according to the authors and/or the test methods. Similar equation proposed by other authors was also discussed.

Crack propagation in metal-matrix/ metal-fibre composites: I. Strength and toughness

The strength and toughness of composites consisting of an aluminium-4% copper alloy reinforced with tungsten wires has been studied by conventional mechanical testing methods and with the aid of fracture mechanics techniques. The effects of fibre volume fraction and of the plastic deformation behaviour of the matrix alloy are shown. Values of the fracture energy, measured in a variety of ways, are compared with each other and with the predictions of existing theoretical models. One of these, modified to take account of the actual shape of the plastic zone developed during crack propagation, has been found to agree reasonably satisfactorily with the experimental results for intermediate fibre volume fractions - ie for composites in which Vf is not sufficiently high to cause splitting and not so low as to permit matrix plasticity to control the composite behaviour. The effect of the matrix work-hardening rate is found to be insignificant in composites containing more than about 12 volume% of fibres.

Frottement interne des graphites

The internai friction of graphites prepared by various processes has been measured using a torsion pendulum (frequency of about 1 hertz) at room temperature. The damping coefficient δ depends on the amplitude in the relative deformation internal between 10 −5 and about 10 −3. For a given deformation, this coefficient increases with increasing tendency of the graphite towards the monocrystalline form. An attempt to check the Granato-Lücke model which interprets the variations of internal friction with amplitude, has not been conclusive. On the other hand, it has been possible to establish a relationship with the conventional mechanical tests (tensile, bending, compression and torsion tests) : the theoretical internal friction coefficient has been calculated using Jenkins' equations describing the force-deformation curves for the graphite. The theoretical expression found corresponds to the general form of the changes observed experimentally. The studies carried out on nuclear graphite show however that the theoretical damping coefficient is slightly higher than the experimentally obtained values. We attribute this difference to a phenomenon by which the graphite adapts itself to the cyclic treatment.