Flexible Follower Response of a Translating Cam with Four Different Profiles for Rise-Dwell-Fall-Dwell motion
The flexible follower response of a translating cam with four different profiles for rise-dwell-fall-dwell (RDFD) motion is investigated. The cycloidal displacement motion, the modified sinusoidal acceleration motion, the modified trapezoidal acceleration motion, and the 3-4-5 polynomial motion are employed to describe the rise and the fall motions of the follower and the associated four kinds of cam profiles are studied. Since the follower flexibility is considered, the contact point of the roller and the cam is an unknown. Two geometric constraints formulated to restrain the unknown position are substituted into Hamilton’s principle with Lagrange multipliers. Applying the assumed mode method, one can obtain the governing equations of motion as non-linear differential-algebraic equations. The equations are solved using Runge-Kutta method. Then, the responses of the flexible follower undergoing the four different motions are investigated in time domain and in frequency domain. Keywords—translating cam, flexible follower, rise-dwell-falldwell, response
Mathematical modelling of layered contact mechanics of cam-tappet conjunction
The paper briefly introduces a fast converging mathematical model to predict the peculiarities of the non-conforming contact between an infinitely long cylinder and a coated elastic substrate. The proposed method is then integrated into a multi-physics analysis of the valve train system of a racing type internal combustion (IC) engine. Due to relatively high loads and speeds experienced, particularly in the cam–tappet contacts, hard wear resistant coatings are used, which greatly influence the contact mechanics performance. Results indicate that the layer thickness is the determining factor in contact characteristics, which alters during the cam cycle. Therefore, for optimal performance coatings of non-uniform thickness should ideally be applied to the circumference of the cam rather than the usual coating of the tappet surface with a given thickness.
Preparing for group analytic psychotherapy: meeting the new patient
Preparing for group analytic psychotherapy—the patient and yourself as a therapist—is apparently done in many ways and still invested with much controversy and ambivalence. Some say, they do no selection or assessment at all. The patients or clients are taken from the waiting list in alphabetic order. Other therapists—mainly those working in National Health Services—use several assessment interviews before including patients into short- or long-term groups. Either way, this article revives some research results about assessment and hopes to inspire therapists in their first contact with the patient by presenting some examples from a clinical outpatient practice in a mental health service.