Search Results

Power shift transmissions used in off-highway agricultural and construction tractors are subjected to rugged duty and the planetary type using needle bearings has proved its reliability when good design practices are followed. This pa per reviews the types of bearings, design data, and applications, and provides the formulas used in calculating speeds, loads, and shaft slopes in planet gears. Discussion of the subject matter by representatives of other companies in the industry conclude the paper.

Lasers are used in the metal working industry for a variety of operations including welding, drilling, cutting, heat treating and marking. This paper will focus on the laser as a marking tool and the resulting effects, both physical and metallurgical, on bearing steels.

This paper addresses a common problem associated with data analysis when a 1st failure in n, Weibull analysis is used. This is known among Weibull practitioners as the method of “sudden death”. Weibull analysis is a widely used reliability assessment and prediction technique. The “sudden death” method was initially developed to help reduce test time. In a “sudden death” test, k groups of n parts each are tested. In each test group testing is halted when the first failure occurs. This is referred to as the “first failure in n” and is usually detected by periodic inspection or by automatic/electronic test shut-off when the first failure occurs. It may happen that the first failure is not detected and there are two or more failures found upon inspection. In such cases the first failure time is lost since there are now 2 or more failures. If the second or third failure time is used as if it were the first failure time, overestimation of the reliability will result.

The behavior of a surface crack that is perpendicular to the contact surface was investigated by using the finite element method. The analysis was two-dimensional, plane strain, and linear elastic. The finite element model was a combination of 6-node triangular and 8-node isoparametric solid elements. A Hertzian pressure was applied at the contact surface. The contact pressure was moved incrementally on the surface to simulate rolling and sliding contacts.. Stress intensity factors were calculated as functions of the position of the Hertzian contact, coefficient of friction on the rolling/sliding surface, and the amount of residual stress in the subsurface. The results suggest Mode I type of growth under tensile residual stresses and Mode II type of growth under compressive residual stresses.

For most rolling element bearings used in practical applications, the permissible speed is defined as the bearing speed corresponding to a certain assumed limiting operating temperature in the bearing. Prediction of bearing permissible speed requires a thermal balance analysis considering 1) bearing heat generation (or torque) and 2) the heat dissipation of the bearing system, which is a function of ambient temperature, housing material and geometry and its heat transfer parameters. Recent results of running torque measurement of needle roller bearings and other types of roller bearings have been reviewed and compared with the well known Palmgren's prediction. The experimentally based formula for bearing power loss for needle bearings is used in the heat balance analysis for determining bearing reference and permissible speed. The calculated reference speed is compared with the DIN calculated reference speed using Palmgren's formula.